Ahem, biting my tongue... the Award-Winning guy put nary a mark on anything, pistons have their con rod bearings/rings intact, engine case has crankshaft in it with that half of the bearing underneath it, other engine case had 3 of the other halves, and one fell out.... I know where they go. You are quite correct that each piston skirt and ring set would have worn in to its cylinder and taking it apart without marking anything was pretty dumb. I would not put it together without new rings, bearing halves (crank & con rod bearings), gaskets, etc. I do not believe one needs new pistons but once cleaned, I'll look closer.
As for the bores, Nikasil plating is thin but hard, newer tech can go 0.002", older was around 0.004", the extremely thin nickel surface part of it wears off quick, so "break-in" is quick. I hesitate to call it break-in except for microscopic "smoothing", I hesitate to even call it polishing (we can't compare this to cast iron bores that actually wear in/bed in). Honing would be too harsh, would ruin it. The original cross-hatching is still there, a testament to its hardness. So here's the dilemma, with new rings, will they "bed in", and perhaps the answer is yes, they are softer than the ceramic (I think). Cost-wise, new Nikasil plating is ~C$1000. New set of engine cases are U$1100, say C$1400+ (Partzilla). Bearings are ~U$100, gaskets ~U$60, new valve seals U$100, assuming one can get away with just a cleanup, which I think is possible.