64 came with the 325hp and 348hp (Tri-Power) 389, they never used a 326 in the GTO. Watch out for clones, in 64 and 65 both years had no GTO designator in the VIN and only the 64 and 65 GTOs built in Pontiac, Mi. and Kansas City, Mo will have the accessory code of 5n on the data plate. Using the VIN You can order the build sheet from PHS.
hi just getting ready to restore a 64 goat with a black interior-what paint is used on#1-interior dash and door panels #2-engine bay and fender wells #3engine(i have seen several shades of "pontiac " blue) #4underside of hood(mine is painted black and it doesnt look stock)-thanks for your time and help-as an old mustang guy its very exciting to finally be working on a GM vehicle-thanks again-craig