I always laugh when I see someone say downgrade.... If you had the money it would be a great transplant
469kW Z31 RB26DETT 300ZX This swap is alot easier to do in the Z31 than it is in the Z32 due to the fact that some JDM model Z31's came with the RB from the factory, you just need the crossmember from one and a few other bits and peices. If you found a 200ZR then the RB26 falls right in... It's not a "downgrade" as such as the RB and VG are both great engines but the fact of the matter is it's not cost efficient for power unless you just want something different. The money it would cost for everything needed and the time it would take is just too much, when you could spend that same money on a stock Z31 or Z32 engine and have a more powerful car at the end of the day.
http://www.prestigemotorsport.com.au/modules/stock/index.php?StockID=4337 yep, thats a crazy engine!~ awesome but... so why spend so much money making a rb26 work in ur zed, when u can get all the power u need out of the original engine