Hi I did just this conversion started with a m600 dark 2000 fitted a 1997 900ss engine problems were
1/ single phase charging on SS sorted by just connecting to two of the where's on reg rec
2/ needed m900 exhaust headers as they are a different length
3/ needed oil cooler and hoses
4/ different neutral light switch wireing needs mod
5/ carbs are same size but different jet sizes use 900 dynajet kit
6/ need m900 inlet manifolds
Engine bolts in no probs if you want any advise just ask done lots more mods aswell