Hi
If you want an RB25 Ceffy, buy the rb20 NA auto Ceffy currently on ebay for less than $5,000 and modify.
Extra cost will be brakes (but you need to go to R33 anyway) and diff. Oh plus hand brake, console and pedals.
Agree it is expensive, although, I did the front mount, 3"exhaust and front bumper at the same time!
Basically have to do water pump, seals and timing belt no matter what and suggest you do exhaust manifold gasket at the same time. All builds up. Also gearbox yoke (need from R33 tail shaft) and fit to tail shaft and speedo drive (as they are different, people use R32 GTR or Navara)
Good luck