Check out VWH and buy their more expensive one. I opted for the cheaper unit as regretted it ever since. I have since returned its faulty carcass and got the better unit.
You need a different pulley for the 70 amp and the cooling boot and possibly even the tin if I remember correctly, unless that is what you already have
AVOID IT!!!!!!! It caused me no end of problems because it started to over charge. Fried: ignition switch, 2 coils, a regulator, points a condenser and fuel pump. Sounds a little at fetched and I may get shot down for it but since I fitted one that is what I had to replace to make my bus reliable again. Go for the Bosch unit. I did look to getting my old one refurbed but the Bosch shop wanted more than a new unit.