I can answer #1. The rear engine mounts (ie: bellhousing mount) in a 49' 216 SHOULD be flat, whereas the bellhousing mounts on the 54' and up 235 SHOULD be angles slightly.
I have seen people cut out and weld in angled spots on their original flat crossmember. If you need, I can take a picture of my crossmember if that is the way you decide to go
