The crankshaft snout should measure 1.125", and the balancer hub should have an ID about .002" or so smaller than the crank snout. If the keyway isn't worn where the balancer can rotate back and forth, just drill and tap the crankshaft snout for the same 7/16-20 center bolt and washer that's used on the 1970-up small block V8 engine. A worn key slot in the balancer requires a new balancer, or another key slot can be broached in the old one. A worn Woodruff key slot in the crankshaft can be welded and re-cut by a good machine shop, but it's an expensive fix that requires a full teardown of the engine.
Jerry
