If you're going to do a swap like this, picking up a USED motor, tranny, and computer is the way to go. You can find setups for $6,500 or so at swap meets.
There are motor mounts available from Street Performance. I think I'm going to go with the AlterKtion front end and have him custom locate the mounts for me to match up with the Hemi.
The picks on that link of the rear trans mount look OK. I don't think they'll have any problems. Unless you're set up to bend 1/4" plate steel, cutting and welding pieces is the only way to go. I did like those custom headers they're putting together.
My latest idea involves picking up a complete HEMI Ram at Salvage Auction, pulling everything I need to do the job, then auctioning off the remains.
Nothing is cheap...but I see it as a chance to do some engineering and have some fun, not to mention that I'll have a pretty neat ride when I'm done.