just to give you an "idea" of the weight differenc, its no where near 100lbs between SR and RB. lets do a test:

with an SR into an S13, the weigth balance of the car is almost 50/50 (with the KA, its 54%front. 46% rear and the SR is around 30-50lbs lighter)

the shipping weight on an SR is 440lbs; harness, ecu, fluids and all

the shipping weight on an RB? 720lbs

theres a little more there than CF hood and moving your battery. and since im probably one of the only ones to drvie one around here, let me tell you once again how much it SUCKS. when you have that much weight of front ti[pping the scales, it doesnt drive right. tire spin is VERY prevelant and just making normal turns in traffic is a real PITA. and THAT car was built on a non-HICAS RB25 using the MUCH smaller and lighter 71C transmission (SR style)

+100lbs for the bigger tranny.

go ahead and do it if you want, but i guarantee youll sell it or wreck it