Totaljdm.com sell Nissna motors. Also, theres place called Noyanusa.com, they sell Nissan motors. I got my H22a front-clip from Noyanusa.com, and the motor was fine.
There is a Noyanusa warehouse in my area. When I went to pick up my H22a from them, I saw butt-loads of Nissan motors, and Nissan front-clips.
RB25DET is that a Slivia, 240, 180SX, Bluebird, or Pular GTI-R motor?
But yeah. both company sell Nissan motors.