my friend had a b20 motor swap with a gsr tranny, so i know getting a b20 block in wont be a prob, and fabricating 1 or 2 mounts for the b20 tranny, and some for the rear dif. looks alot easier than chopping out the back of my car and doing what your talking about. also looking into which way takes less welding. and by far, i think putting a motor in the back takes alot more welding and shaping sheet metal. with my luck i would get it done and the body would be warped and would flex alot because of the giant hole i tried to cut and patch. either way prefer my motors in the front, not trying to build an NSX, that thing probably hold has much coolant as it does gas....! haha not really but it does take like 10 gallons of coolant