There's is a few options about, if your pockets are deep then tractive is one of the ones to go for but if not then selholm and elite to name a few , I had a g33 quaife which I sold before I used it has I heard some stories and it turns out after I sold it the bloke used it and quaife built it wrong ( 5 and 6 the wrong way round) and then charged for new gears. But I am looking at going elite but just waiting to see what some other people think of them that have them in production cars ( ie not kit cars) but I hear that they alone with selholm change gears nice and the tractive is very smooth