I would say that it's toast - don't even try to fix it - replace it.
Find out WHY it happened. Check that the crank thrust bearings are in the correct location (a FE has them in the centre mains bearing position, possibly the Windsor block has them there too) - and that the engine wasn't rebuilt by some Chevy rebuilder who put them in the 4th mains bearing position instead of the centre one...
It's likely that if there was that much play, you will need to check the auto trans input shaft/torque converter and the waterpump too.