I'm coming late to this discussion - the OP said the clutch rattled - but did not say the tractor fell in half - just a couple bell housing holes had broken out. The housing is ductile die-formed mild steel, easily weldable.
For now I'd suggest a low cost repair - putting a temporary brass (or oilite) sleeve around the shaft, with the other end mostly filling the worn crank bore acting as a pilot bearing. It won't be a perfect fit, but it will be trapped in there and should tighten things up enough to operate with much less clatter.
You could make a couple retainer clamps to help hold the cracked housing to the block. Attach them with the same bolts - but do any welding on the housing AFTER the bolted clamps are tightened, holding it in place.
With this kind of alteration making the machine usable, put some hours on it to see what else it might need before deciding whether to dive deep.
Take care, Dick B