360 trouble. please help

5 degrees initial timing is what the factory set the initial timing to. According to you it has a much bigger cam than stock and that requires a lot more initial timing to run it's best (mainly affects idle and low speed performance) so as the others said the initial timing needs to be a bare minimum of 15 degrees. Personally I'd set up the distributor for 20-22 initial with 12-14 degrees of centrifugal advance in by 2500 rpm which would give you 34 degrees total timing. It's possible that when you got the car someone jacked up the initial timing without re-curving the distributor in which case the total timing would be wayyyy too much and possibly cause the misfiring you mentioned. It can also damage the engine

I remember reading an article that shows step by step how to re-curve your distributor but now I can't locate it. Anybody else remember that article to post the link. It was one of the magazine's that put it out. Possibly Hot Rod??