850 crankshaft flywheel, refitting cranks

You make marks before disassembly which look to be missing, the last time I came across this I carefully looked at the marks on the flywheel flange and crank ends and was able to match them as the oil burnt stains were mirror images. Before you do that look for a T on the outer edge of the flywheel and that should be the timing side.

Maybe photographs of used cranks on ebay will give the necessary info ?

There was a thread on access Norton with pics of cranks trying to work out differences to see if the flywheel was always one way, the cast surfaces were all over the place in relation to the machined datum points. So looking at pics leads nowhere.

The early Dominator engines had a T, S or Z stamped on the edge of the flywheel.  As a rule this was usually found on the Timing side of the assembled crankshaft. Likewise, these Norton chunks generally came with a casting number which also usually faced the Timing side.  See Photos.

Back in the 1970s the Norton factory was boasting that their modern machining methods were so good parts such as crankcase halves no longer needed to be matched, Silicone Goo was replacing thick gaskets and the crankshaft flywheel could face either side of the engine.

In my experience, parts distort with aging and dismantled chunks need rebuilding with matching faces. The latter always seen as good engineering practise.