[Dan72cst]

I'm not a "guru" but I believe they will bolt onto your '81 block. BUT MAKE SURE YOU HAVE THE CORRECT PISTONS. Big blocks have closed chamber heads and open chamber heads. They have to use pistons designed for closed chamber or open chamber. NO if's and's or but's !!!!!! I think GM changed from closed chamber to open chambers in 70 or 71 except for the vette changed to open chambers in 69 or so. You'll have to ask a guru for exact.