i don't see a problem with helicoils, but i'd rather see and SS bolt welded to the frame. i've used this several times with no problems. i'm also not big on that sw on the ground cable, i'd be on the + side and kill the battery for everything and run grounds from engine to frame and put in a ground block under dash to use for gages.. just make sure the engine ground is lg nuff. u can get away with a #10 on the dash grounds. of course ground the battery to the frame where its at.. also make sure frame to body is grounded.... grounds everywhere ain't gonna hurt nut'n.
also don't the optima bat's need another (regular) battery in paralleled to be able to charge it ????