Are you sure that is a OC-3 frame? Most of those problems were on HG's. The later HG's and all oc-3's were 'beefed up' on the rear of the frame. There was also a field modification for the HG frame which reinforced the area around the bellhousing, the forward section, and the rear section was reinforced by welding a bracket to the frame which added ridgidity via hickory blocks and u-bolts. Like John said, it would probably be best to see some photos.
Take care,
Andy