my dad and i just cranked our 383 in the duster. motor freshly rebuilt. everything new. we are getting plenty of fuel, and the dist is getting spark. we are getting backfires through the headers, and no firing. we messed around with the distributor a bit to make sure it wasnt a minor timing adjustment, and still nothing. we swapped the wires 180 degrees and got backfire through the carb. any input appreciated.