[70rs/ss]

If you can get the engine crossmember (73 and up)as well it is a bolt in deal, but the clamshells can be bolted to the 69-72 blazer crossmember I think, just drill the holes into the existing crossmember and bolt them down. I'd guess a wrecker would sell the whole crossmember cheap and the clamshells should be replaced (inner rubber bisket gets soft), an OE type clamshell can be had for $20 from the cheapy auto parts stores or a urethane bisket can be bought and inserted into the clamshell (opens like a clamsheel and the bisket drops in). LMK if I can help any more. In a 2wd the 73 and up mounts can be bolted to the 67-72 frames and used for a SBC or BBC install as well.