Were talking 273 motors....all other parts be damned. Early heads had the weird 5/16 intake bolts with their angles. Thats all. IIRC 69 273 was supposed to have hydro lifters but they seem to be pretty rare. The cams changed a little as well as compression ratio but the blocks were all the same.
Yes to the early intake bolts. 68 and 69 had hydraulic lifters and non adjustable rockers. As fas as blocks there were 3 or 4 different casting numbers. I don't know what the differences are between them.
