Gearbox modification on hybrid 2.0 long block GTi

I have an '89 Golf GTi Mk2 5 door (small bumper). Originally it was competely standard. Since then I have made many modifications. These include, K&N induction kit, mongoose full SS exhaust, 4 branch manifold, brand new bored out 2.0ltr 8v hybrid long block GTi engine, ported/bench flowed head, vernier pulley, Kent stage 1 cam & 60mm lowering SPAX.

I have just run this thing in and it goes like hell. The problem is, the engine produces sooo much torque that the gearbox is falling to bits and is desperately in need of replacement before it explodes and locks up the front wheels!!! NOT GOOD!

It has been suggested to me that I just get a 16v gearbox or another 8v box and chuck it straight in, however, now I have the extra power I was thinking of somehow making every gear longer with out loosing the 8v gearing configuration as I believe this is better for low end torque. I assume this would mean increasing the ratio of the final drive gear in the box.

My current box gives around 120-130mph. I need a top speed of around 140-150mph.

Is the 2.0 Ltr 8v Mk3 gearbox longer and would it fit to mine? Or maybe you know of another car that has a longer/stronger box that would fit.

Cheers,

vwjim2003