a stock gearbox will cope for a while, engine would need a few bits to be reliable but not crazy money should be cheaper than a yb and cos 4x4 box mods but the rb26 and box will carry a weight disadvantage.

when a healthy stock rb26 at stage 1 will make upto 450 hp it shows how easy 650 hp will be attainable compared to a yb but rb26s always seem to lack in torque I think due to being a short stroke, they love to rev though and have solid lifters stock.