Have you tried bolting back on the flywheel, then using a couple of vise-grip pliers locked onto the flywheel and wedged against the block to prevent the crank from turning while you torque on the tap threaded into the old bushing?
I recall somewhere back in time where Jerry "Hotrod Lincoln" suggested something along like this crank immobilization method, to hold things steady while you do the removal process. I just couldn't find the specific thread where I saw that.
