the only part you need is the outer carrier bearings for a 90 toyota 4runner 4x4 front diff. other then that just seals, and all other normal items for a diff rebuild minus the parts to rebuild the stock lsd's. as for strength, i did a little searching, and the truetrac is designed for 4x4 trucks as we already know, what most of us dont know is with the r&p gear ratio some of these trucks run, plus the power going through a tranny and a transfer case, it is possible to see up to 1400lbs/ft tq at the wheels. now, since most of the higher output mkii's are going to be in 400lb/ft tq range i dont see it as a problem. i personally am shooting for over 600rwhp when i build my other motor and dont think i will be able to break it.