THE UPPERS ARE CHEVELLE 64-72 .MONTR CARLO AND GMC SPRINT 70-72.////////////THE LOWERS ARE 70-72 WITH 6 CYL AND SMALL BLOCK ENGINE.//////// IF YOU HAVE A BIG BLOCK ENGINE THEY ARE SAME 64-72. ACCORDING TO HOLLANDER INTERCHANGE MANUAL 42ND EDITION. THE EARLY ONES AND HEAVYER ONES FROM A BUG BLOCK ARE SAME DIMENSIONS AS THE NEW LIGHTER VERSION FOR SMALL BLOCK AND 6 CYL CARS. LEARNED SOMETHING TODAY NEVER KNEW THERE WAS A DIFFERENCE.