well i have 1964 grand prix was a original 389 car with an auto been trying to find a runner to put in it came across a 71 350 firebird engine but that fell through ..

Kazulin, First off, please read my reply to your other question. If the 66 389 is OK, and if the turbo 400 transmissionis anywhere close to being OK, I would use that combination. Even if the transmission needs work it would probably be less expensive and more trouble free in the long run. The marriage of the 66 389 to the 64 automatic would be rather difficult and trouble prone. Good luck with your project and keep us informed.

Kazulin, Possible trouble spots using the turbo 400 in your 64 GP would be the trans hump ? driveshaft length? trans output u-joint? trans cooler lines? electric operated kick down on the turbo 400, trans cross member mount?........Bottom line,this is not a direct bolt in, but certainly very desireable and do able. Enjoy the project, I will long distance help you if I can.

that sounds like a good combo but i had the same combo in my 65 gto and the starter mounts to the engine not the tranny , the only other car i've seen where the starter mounts to the tranny was a buick. that combo will work but you will have to buy a pontiac starter that mounts to the engine.what happened to the original engine ? the only other issue would be the drive shaft. if the shaft is too long ,no big problem you can have it shortened, if its too short you will need a new drive shaft. the engine and tranny will bolt right in without any mods. good luck.