Need help on a V8 swap

You don't have to change the frame, but it will cost you a chunk of change to get conversion mounts, depending on if you have biscuit or spool mounts, since you have the 73+ K member, might as well use it, the spool mounts are far superior to the older ones.

Summit sells conversion mounts, as well as a few others, schumacher creative services comes to mind, or you can roll your own, like I just got done doing this week.