In the days of my ERST i went through quite a few boxes, i ended up buying a BC box out of a TD van and had it rebuild with an s2 slipper.

I cannot remember what the box was out of, but one of the late turbo diesel boxes can take a lot of punishment. I think it has some bad ratios in it so swap them with those from a BC ERST box (i handed over an erst box and a diesel box and the guy just made me a hybird). Think he only charge me about £150, that was 10 years ago. Sorry i cannot be specific it was a long time ago but it lasted and I was running close to 250bhp.