Transmission adapter to mate a slant six to a smallbock trans

I never got that far along with one of those adapters, in bolting it up to the back of an engine, and then mating up the transmission to the adapter.
Due to the thickness of the adapter, wouldn't you run into problems in trying to bolt down the transmission into the rear crossmember with now everything being longer?
Was there a different transmission mount also for that set up?
I always wondered about everything working, linkage, mounts, stuff like that.
Sounds like you know lots about this stuff.
Why don't you just go and find a slant 6, 727 transmission?
Wouldn't that be a lot simpler?