How can I say I hate you? LOL That is some serious work. As for the intake thingy for the RB25... yeah, I looked it up for the RB20... I was looking at another $800-ish. I still have ideas for the future building. And if I had the luxury of time/money that you apparently seem to have, I would do a better build. But seeing that my S12 is my daily and I want this thing finished by HIN, Sept. 30th, I have to settle with some things left undone and to be finished in the future.
You shouldnt have too much trouble. Your tranny will actually FIT the confines of the 200sx tunnel, and you can use the R180 (I just didnt want to).. Hints for wiring:
a) Use the 200sx lower engine harness
b)locate the oil pressure signal wire in the cluster. Wire it to the ecu
c)locate the 200sx (chassis side) clip that contains the fuel pump relay signal.
d)you will need to switch (via the ignition switch) the ECCS relay and the Ignition relay. The ignition relay charges more than just the coilpacks, read the diagrams.
e)If possible, upgrade to a 240 radiator (or better). You will not be able to fit the clutch fan, so find some alternatives.
f)Fitting in a downpipe around the steering column is hell, get a pro to do it.
g)You may have to cut the hood bracing to clear the throttle body
h)Oil filters are the same as the KA24
i)Check the water pump for corrosion (internally).
As for money, I wouldnt really say I have alot of it. Moreso that I save up for key components which I think will vastly improve this project's all around performance. Almost no money is being spent on looks or interior (It will have no interior).
Today I realized (horribly) that the 240sx front shocks are not going to fit. The springs are too large of a diameter. I do have Nismo 180sx struts on the way, but I believe that I will also need to order a set of Ground control coilovers to adapt to them.. More time/money into the mixing pot.