On a 73-76 small block k-member to big block Schumacher kit you CANNOT go back if you decide to. That kit requires shortening the driver side motor mount saddle. Spend your money on Schumacher if you want to. I'll save that money for other parts.
When you go back, you just weld the piece back on. Its better then trying to move both mounts back to there original position the way you do it. There is nothing wrong with the way you do it. It is just easier to install a big block with Schumacher mounts, even when you decide to change it back to a small block on the 73 -up. On the 68-72 A-bodies, just change the motors mounts and your down. Now for only $160, Schumacher mounts is the way I will always go.
