Is it a new engine build, did you disturb the OIL PUMP ?
Have seen it more than once, try it without the dizzy/oil pump driveshaft, bet it will be ok ?, if so the oil pump doesn't always sit 100% perfect on the dowel, and this gouges the alloy casing of the pump as it's tightened down, so a bit of fettling with a file to grind off mashed edge that sits around groove is all that needed on base of oil pump, only ever had to shorten 1 driveshaft.
The last one the dizzy would not turn, as the pump was seized due to not sitting 100% on the dowel, this jammed the drive part which goes through this dowel, so as the pumps jammed you can't rotate the dizzy as the shaft stops it.
Just make sure there are no flat sections on any of the teeth on the dizzy drive cog and jackshaft drive cog.
The dizzy drive cog is different to a pinto one, so can't use one of them if needed, but I have spares(a few), I always mod the dizzy top bush to oilite bush, as the crushed iron particle bush(std) is crap.
tabetha