With a rb20 trans, you could just use the stock rb20 mounts and 280z tranny mount and stock drive shaft and a rearsump oil pan and pickup from nismoparts.com . My friend and I did it with his. It was a very simple and straight forward swap. It was an rb20 but then it blew a ringland and he put an rb25 in it a couple of weeks later. I assume he just swapped the long blocks. But for using the 25 trans you need a custom tranny mount, or mountkit and a custom driveshaft. I would say get an auto rb25 for 1100, rb20 trans for 250, rb20 mounts $50, oilpan n pickup for 200, clutch for 250 flyweel for 40-100, and be on the road for under 2k.