Be careful buying a six speed box for a vx, depends what your final drive ratio is as i think 6th is 1 to 1 ratio. same as 4th in a t9 ford box. Unless you rev the bolx of your engine this will seriously limit top speed. Revs are what kill the standard t9, suffers from oil starvation on the main shaft at much over 7000 rpm. I'm running a close ratio straight cut box built by competition transmission services in luton. Go for the heavy duty quaife kit.
If you speak to bernie at cts he can advise you on exactly what you need and wont rip you off.
www.gearboxman.co.uk/