# 1968 GTO convertible restoration issues



## mrvandermey (Jun 15, 2011)

Hi guys, it has been awhile but I am back. 

I am working on a '68 GTO convertible and I am running into a couple issues.

1) I discovered that if you want non-hide-away headlights, that you may be in trouble. I discovered that no one makes reproduction non-hide-away headlight bezels or mounting plates. I was going to use hide-away mounting plates and then modify it to work. However, I just scored a complete see non-hide-away headlight assemblies in excellent condition, so that issued is resolved.

2) I also discovered that coupe rear quarters have a different contour at the shoulder than convertible quarters. Of course there are not any reproduction convertible quarter panels out there. Does anyone know where I can obtain a set of 1968 (or 1969) rear quarter panels?

3) Another issue I have is the rear end. If I am correct, in 1968 you could only get the 10 bolt, 8.2 inch rear end. Now I have heard rumors that a GM 12-bolt isvthecwaybto go. Bytbthen I was told a Pontiac 10-bolt, 8.5 inch us stronger. Now I have heard that the Pontiac 10-bolt, 8.2 inch is the best way to go? Also in gears.....I have been told in the past that 3.55 or 3.90 is the way to go. Now I hear 3.31 or 3.23 is better. So my question is what is truth and what is rumor in regards to rear ends and gears?

4) What is the best transmission to be used with the Hurst dual gate shifter, Turbo 350, Turbo 400, or either will do?

Any tips, advice, or etc would be highly appreciated.


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## BearGFR (Aug 25, 2008)

mrvandermey said:


> 3) Another issue I have is the rear end. If I am correct, in 1968 you could only get the 10 bolt, 8.2 inch rear end. Now I have heard rumors that a GM 12-bolt isvthecwaybto go. Bytbthen I was told a Pontiac 10-bolt, 8.5 inch us stronger. Now I have heard that the Pontiac 10-bolt, 8.2 inch is the best way to go? Also in gears.....I have been told in the past that 3.55 or 3.90 is the way to go. Now I hear 3.31 or 3.23 is better. So my question is what is truth and what is rumor in regards to rear ends and gears?


"It depends". On a stock motor driven more or less 'civilized' most of the time, the factory rear is more than adequate with a quality rebuild using good parts. Behind a significantly "enhanced" engine driven with "gusto", it won't live long. Personally I favor the 9" Ford in that case. I bought one from Moser, turn-key and ready to bolt in, and it's the one part on my car that I didn't have to modify in some way to make it fit. Gear ratio is a matter of how you're going to use the car. Anything 'more' than 3.50 is going to be marginal for any kind of highway driving. The Beast is showing 3200 rpm on the tach at 70 mph, and I'm running P275/60-15 rear tires. 3.90 (and 4.30) gears were used usually only behind the Ram Air IV which was a high rpm engine and needed the gear to get up into the power band. For street cruising, occasional highway use, and occasional racing - 3.50 is about the limit in my opinion. 3.31, 3.23, or even something in the 2.70 range is better for ecomony and highway. We're dealing with Pontiacs here, not chevies --- Pontiacs make enough bottom end torque to be happy with just about any gear and still provide plenty of fun. This is more of a 'how are you going to drive it and what matters to you' question --- there's no one right answer.[/quote]



> 4) What is the best transmission to be used with the Hurst dual gate shifter, Turbo 350, Turbo 400, or either will do?


My opinion? Nothing better than the TH400 to stand up to Pontiac torque. A TH350 can be built strong enough, but the weak link is the case itself if you start hitting it regularly with 500+ lb. ft. However, the TH400 weighs more than the TH350. This is more of a 'what will live best behind my engine' question than it is a 'what works with this shifter' question.

Bear


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## mrvandermey (Jun 15, 2011)

Bear, thanks for the information. My car will be a boulevard cruiser with the ability to be respectable in the occasional bout of competition with a Mustang, Camaro or Challenger. So I guess a posi 3.23 might be in my best interest. As for what rear end, I expect to have between 400-450 HP. So I am still not sure which rearend to use.


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## BearGFR (Aug 25, 2008)

At that power level, you're sort of on the borderline in my most unofficial inexpert opinion. A well built 10bolt might be fine, one with a defect in the case or that wasn't built using good parts might not be. You've got a little "buffer" there with the automatic since it won't shock the drive train like side-stepping the clutch to launch the car on a manual would. Your situation is sort of one of those "do ya feel lucky?" propositions. If you want a guaranteed (near) bullet-proof axle that you don't have to worry about ever, then get a good 12-bolt or 9 inch (and get your check book out). Otherwise, go ahead and rebuild the factory 10-bolt using the best quality parts you can find, and see how it goes. Traction plays into the deal too. Street tires that can't really "hook" a Pontiac tend to save the rear end. Good sticky drag radials or slicks on a car that makes lots of bottom end torque tend to accelerate its demise.

Bear


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## ljsflash (Nov 30, 2012)

mrvandermey said:


> Hi guys, it has been awhile but I am back.
> 
> 
> 
> 2) I also discovered that coupe rear quarters have a different contour at the shoulder than convertible quarters. Of course there are not any reproduction convertible quarter panels out there. Does anyone know where I can obtain a set of 1968 (or 1969) rear quarter panels?


I'm running into the same issue. Did you come up with a solution? I've talked to a guy who did use the coupe quarters for his '69 convertible. It turned out beautiful but it was a lot of work and he's prob. the most experienced GTO resto guy in the country. 

I could probably get by with a driver's side door jamb and a quarter skin but I think that I'd rather have the whole panel.

LJ


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## mrvandermey (Jun 15, 2011)

ljsflash said:


> I'm running into the same issue. Did you come up with a solution? I've talked to a guy who did use the coupe quarters for his '69 convertible. It turned out beautiful but it was a lot of work and he's prob. the most experienced GTO resto guy in the country.
> 
> I could probably get by with a driver's side door jamb and a quarter skin but I think that I'd rather have the whole panel.
> 
> LJ


I resolved my major rear quarter issue by trading the rusted car out for a car with minimal rust issues.


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