What i did was have the gearbox fully rebuilt by hotgolf and the flywheel was lightened / balanced at the same time, so the longer top gear has not taken anything away low down in the revs (because the flywheel spins faster now its lighter)
the wavetrac diff and ARP bolts were near £1000 with the Vr final drive
not a cheap game mate
top speed on my old 16V gearbox was 150 on the dials, the new top speed is greater, iv had it showing 160!
but how reliable the read out is at this speed is another story