I think you're about 30 years too late chap.
I had an accident around 13 years ago that wrote off my '92 851 and there was almost nothing available for it back then.
Fortunately for me I'd already stocked up with some spares that I thought might become NLA and the good members of this forum donated the parts that I was short of to get back on the road in double quick time.
An awful lot of the internal engine 748/916 parts are interchangeable with the 851/888's. To this end many, many years ago I bought 900 Monster wheels, swinging arm and a 916 motor to cannibalise for spares if and when they were needed.
…and that's part of the reason that I 1st ended up with a 916cc 851.