I have made some mounts for a 61-64 caddy, that are a bolt in with shock mounts, they worked out pretty good. You could weld in if you prefer. Anyone can email me about them if you like:
nolimitscustoms@hotmail.com. We can talk about making you a set or I could lead you in the right direction to build you own, I have full install instructions as well.
Later, Clint