Anyone ever consider this swap in the '73 - '87 ('91) body styles? Are the mounts on the 8.1 the same as the 7.4? I had heard a rumor that GM cast two mounting locations on the block and that you could use the second set (matching the 7.4). Anyone know if that is true? Also, how would one mate the Allison to a doubler. Any suggestions would be most appreciated.