I have a 1981 Custom Deluxe with a 454 big block?

and recently i let my dad borrow it and he changed the dist. cap and took it on the highway, but soon came back saying that it was coughing, and back firing? he said that he pulled over and checked the distributor and it was loose.BTW the engine was running great before any of this happened!! Now I'm trying desperately trying to get the engine back into its factory setting timing, but i cant? i checked the firing order, plugs. and now another problem the engine i guess is to heavy for the starter i've had to replace one already! please help! is it true that the cables play a role because the driver side is touching the headers?