# Trying to find a correct 389 for my 65 GTO



## Indy1K (May 16, 2008)

I just purchased a 65 GTO that has a 428 in it. Other than that, it is an all original 65 2dr. Hardtop, 4spd, PS, PB, A/C. even has the original Blue Charcoal paint. I am looking to replace the 428 with an original date code correct 389 4bbl (WT block)
My cowl tag shows the car being built the second week of December (12B-1) it also reads 65-237375P, so it was built in Pontiac. 
My question is what should I be looking for? 
I know it is a WT block, but casting date? Block unit # ? or is there a VIN or serial number? 
When would it have been made? December of 64 or December of 65?

Thank you in advance.

Kevin


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## O52 (Jan 27, 2019)

If the car was built in Pontiac then the engine should have casting date of the first week of Dec 64. The engine plant was next door to the Pontiac assembly plant. 
Engine assembly usually followed the casting date by 1-2 days. Then moved or shipped to the assembly line. EUN (Engine Unit Number) is normally dependent upon the assembly date. VIN stamp didn't appear until the 68 models. The EUN is the blocks serial number. 
When you order the PHS documents for your car it should show the EUN. (early 64-67 models primarily)

Now with all that being said, it is not unusual to have a block casting date 1-3 months before vehicle build date. If a block or other components had defects after casting they would be repaired if possible. Then added to engine assembly line afterwards.

Wallace racing has a partial listing of EUNs to Casting Dates
An engine cast on Nov 24, 64 has EUN 122392
Dec 8, 64 has EUN 143224
Dec 11, 64 has EUN 167123

as an example of a late assembly date;
Cast date of Nov 20, 64 has EUN 190212


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## Indy1K (May 16, 2008)

Hi Ed,
Thank you for that comprehensive response. Unfortunately, the PHS docs I got are copies and only partial pages. I have re-ordered a new package from PHS
Best Regards,
Kevin


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## 1971LemansWisc (Apr 18, 2021)

Kevin - Congratulations on your purchase!

Very Cool - huge fan of Blue Charcoal.

Just looks really good on the 65s!

Randy


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