Will not start it has spark turns over backfires through throttle body

Truck will not start. It has spark turns over backfires through throttle body. Changed plugs sounds like out of time. Not familiar with this year distributor. Loosened distributor to see if it was only a tooth out. Does this have a module in distributor like the old electronic ignition? Chevrolet's used to have if so could this making a backfire through the carburetor like it is at a time.