the twinky can go just about as far as you acn take it with an exhaust (from ashely) and filter (from K&N) and cams (from piper)
but thats about it unless you start talking about getting it blown or fitting nitrous

the box will take the increase in power, and if it doesn't you can always get one from a 2.9 grany and convert it to fit

as far as stopping and cornering goes you can use cossie stuff but watchout for the different sizes on the rear shocks and the different hubs on the 2wd cars
the 4wd stuff won't fit on the front, be they struts or discs