Slabby 750 engines have dif inner dimention than short stroke, them component s dont exactly work on the other. There are kits 884 iirc or maybe you still can find rare racing parts.Racing slabby s went 130bhp
Whats wrong with the vm29ss? If you want to keep the airbox, carbs from a 1100 powerscreen fit right in. If you dont bother about the airbox, cv,s bst36 are the choice, or rs 36 if you go mechanical flatties.
11/12 have the same height, the 1100 exhaust will be fine, as for height, but you have to check if it clears the sumb, a dummy fit will do, otherwise you have to change sumbs or use a 1200 exhaust that you will need mod at the midden/rear mount.