the 340 motor in my original 68 formula S had an edlebroc alluminum high rise manifold, hooker fenderwell headers, a holley 750 dp carb and a "viscus drive" clutch fan. other than that, it was stock - all the internals were OEM. my "Sun Super" Tach had its red needle set on 6k but in many a street race, the needle was still moving when i would power shift. except for the 69 Z/28 302, there were very few engines other than the 340 that would go to 6k on a regular basis without a serious risk of a BIG BANG coming from under the hood.