i just bought a 66 340 for my 62 F/85 cutlass and when i run the numbers i come up with a 340-4V-260hp, the one thing i can't figure out is the head numbers say they are a 66-300? is this correct? or did someone change the heads long ago? and if so why? it looks to be all numbers matching, meaning both heads have the same numbers and it all has the same date codes within a day of each other, also i can't seem to find the intake or exhaust manafolds anywhere. this is my first buick i'v owned so any info would be greatly appreciated. the numbers are as follows, BLOCK-1374557F, 243 MB, HEADS-RIGHT SIDE-B1376330J M-18, LEFT SIDE B1376330J M-17, INTAKE-B1374559E L-27, EXH MANIFOLDS-LEFT SIDE-B1375907 M-10, RIGHT SIDE B1375912, please let me know anything anyone knows about these and if it's worth my time to even rebuild it, i'm planning on boosting the hp as much as i can with just a hop up kit, i only gave a 100.00 bucks for it and it came with everything from pan to carb including PS pump and altenator, all brackets and starter, i thought is was a good buy, thanks for anu help anyone can give me.