The photo below shows the motor mounts that I have. They mount to the engine in three places. What did you do to move the mounts? Did you cut a new slot in the frame? Or did you cut slots perpendicular to the one that's there?
I'm pretty sure in Wayne's thread he mentioned moving the mount location by a 1/4" I'll have to look through his thread again.
If your keeping yours NA how are you routing the exhaust? Moving the engine back will leave a little room between the frame and the heads. One possible route would be route the headers buy the side of the motor mounts keeping it tight to the heads and then over the axles. Under the frame is unacceptable, no ground clearance for that. Through the motor mount mounting bracket may be an option if notching and reinforcing the frame was something I was willing to do. That would run the exhaust under the axles and right up against the tranny. Or just run straight pipes out the side. Lol anyway just thinking out loud and rambling, any ideas will be appreciated.