It needs to be done in a lathe. You will need to make a fixture from an old connecting rod. Done it many times on 250's and 292's. You also need to make sure the GMC rods also were machined with a radius back in them after they were narrowed or that will also cause you problems as well. You may also have to narrow the bearings since the GMC bearing is wider than the Stovebolts. That conversion is a little more involved than is realized.
