[Mike Jones]

Easy enough to add a ground from the block to the frame. Have someone hold the key over, while its hot, feel positive and negative cables for heat. Hard to believe all those starters were bad. Long stroke Caddy engines from years ago would have a problem when hot caused by sediment that choked the bottom of the cylinders. The motor would turn, but slowly. Batteries, cables and starters wouldn`t solve it The fix was to knock out the freeze plugs and clean it out, the best you could. A s**t job that you crossed your fingers on, lol. Be glad you won`t have to do that!
Good luck