having trouble with circa 1978 thunderbolt ignition on 454 bbc. some kind of disc trigger nobody seems to have seen before p/n 332 3984A33 ? Wondering about MSD 83606 ready to run distributor or 8560 with 6M-2 cd box and coil? Want to be sure I am going upgrade and not backwards. you all have been very helpfull with new heads on my 350 and cooling 350, so I am asking again. So, what ignition system for older 454? Thanks, Bob. Also, Does anyone have expierence with the MSD #83606 ready-to-run distributor with CD built in?