Has anyone used these connectors? P/N C 3115 at Summit. 1970 Dart. They are about $40 less than the Mopar Perf units. They are a bolt in, with 6 bolts per side. I wonder 1) If they are strong enough? 2) Should they be welded in, after installation? To make it more rigid. Does that help? 3) How do you remove the undercoating around the weld areas? Heat it with a propane torch, and then scrape it off? All suggestions, comments are appreciated, . Thanks!