Well, having examined things a bit closer it seems that the flywheel I had was skimmed to half its original width, so I used a spare one I had lying about. Had to mark and drill this. I will most likely end up grinding the end of the crank and using the spigot supplied. The engine is not destined for anything else and, after a bit of measuring, it seems like a bush inside the V8 crank wouldn't be very big. Incidently, my gearbox shaft fits inside the V8 crank with a bit of room to spare.