need some timing advice please!

I've got a 318 Magnum (carbureted) in a 46 Dodge pickup,and I'm having some timing issues. Tried a Pro Comp distributor,by the way,and couldn't get that to work at all. Put on a regular old Chrysler dist. and wired up a GM HEI ignition module,and it fired right up and runs good,except when I hook up the vacuum advance and rev the engine it backfires through the carb.If I advance the timing way way up it runs nice,but kicks back when starting it so it's way too advanced. i can leave the vacuum advance hose unhooked and plug the carb port,and it seems to run good at about 10 degrees advanced. As soon as I hook up the advance,can no longer get it to rev up. I just dug this distributor out of a 440 that i had sitting in the shop,so don't know much about it,other than it seemed to run ok in that. Just feelin like an idiot here,what am I missing?