also about u questons about the S-15 going into a G20, good luck man, the G20 is FWD and the S-15 is for the the Japanese Silvia, which will fit perfectly in the front of a U.S. 240SX. your questons about the tranny's the S-15 Silvia is the only SR20DET with a 6-speed manual, which started production in 1999, and everyother SR20DET came with a 5-speed manual. it is easily possible to put the S-15 tranny on earlier SR20DET's like the S-13 and S-14, or otherwise called the Red Top (S-13). i wouldnt recommend the 6-speed if u are planning on moding the SR20DET, because they are notorious for breaking gears under high power. also if u are getting a 89-94 240SX from your grandma, i recommend u check out
www.unstable-hybrids.com for engine swap info, but like i said earlier, if your going to mod it, its not going to pass emissions or smog. also for everyone information, the SR20DET is not the only engine that is swapable in the 240SX, the Skyline GT-R's RB26DETT is a possible swap, and unstable-hybrids is the guys that could do it, they also did a RB20DET swap in a 1st gen 240SX that was at the NOPI Nationals, it was fuckin sweet!!! to youngster, dont get me wrong about the 6-speed tranny, i have one installed on my Red Top SR in my truck and it works flawless, but u cant mod the motor or else u will pay for it! good luck, and hopefully u can get the swap of your dreams come true.
P.S. MotoRex in Gardena, California (the only Skyline dealers in the U.S.) has been workin on bringing the SR20DET's over and making them street legal while being heavily modded, u should look into this when it becomes available!:sun: