Easy to check for a bent crank, just put it together without the centre cap.
Try it with and without a shell in the block...
If it spins without these, the crank could be bent - Just put a dial-gauge
on the centre-main and turn the crank. Any wobble will show on the clock.
CHECK THIS: I read somewhere that the factory would let cranks be fitted
with as much as 4 thou of bend in them. (Vizard, probably...).
If it still won't spin with no cap, check that it has it been ground the same
size on ALL journals and that the shells match? I have read of some really
dubious practices along the lines of only reboring one pot, so it's possible
that some people would only do a part-regrind...
As regards the orientation of the caps, I was told recently on here that
the tags ALWAYS go on the same side s each other. I normally stamp
dots on mine so I can see from the outside that I have done the assembly
correctly when I am worrying about this later on...