That bike has a later model SS swing arm and hugger on it, same as my bike. You can see the pinch bolts in front of the pivot pin and the attachment of the hugger to the swing arm. Possibly has a later model 750 motor in it also, as the c/s sprocket cover is grey, like the later versions. If your motor blows up, its the easy route to get the bike back on the road. Lots of cheap 750 SS and Monster motors out there.
Cheers, Phil
Duc in the Bay
1990 750 Sport x2-Rosso Blanko (900ss copy) & Nuovo Nudo (Scrambler project)
1991 907 -mostly stock
2002 ST4s - Lots of mods.