Continental A-75 hub torque

Good question. Make sure it's tight and then safetied with a small
bolt and castellated nut when you put it on. No beating,whacking, or
hammering. Don't wallow out the rod holes in the hub nut. Use a
snug-fitting long rod. The crankshaft is tapered. So is the female
hub.

Those crankshafts and hubs should also be magnafluxed before being put
back into service. The keyway for the woodruff key is susceptible to
cracks. Have you checked for cracks?

Also make sure you have a lockring which secures the nut to the hub, or
when you remove the hub down the road, you'll have the devil getting it
off. I don't know how many of those hubs I've seen without lockrings.
Check the hub for runout.