1974 Dodge 360 W100 Backfires

[jb77]

Hello All;
I just finished doing a required lower end overhaul with a stock new cam & lifters. I made very sure that the timing chain was installed right. I had Recarbco out of Pittsburgh, CA (www.recarbco.com) rebuild the Carter 750 4B carb, it was leaking from the secondary shaft in the outside wall; and by the way they did one excellent job, highly recommend them.
So after I get the motor started and running, there is and backfire/miss thru the tailpipe. Here are some of the facts:
*Dodge 360 (1974) bored out to .030.
*Carter Competition 750 cfm 4b, rebuilt.
*New stock cam that came with the master overhaul kit with lifters.
*All of the modules, resistor, control modules have been replaced.
*New cap & plugs.
*Old rotor and old wires.

Does anyone have any suggestions on what to do?

Found the problem, after checking the firing order for the forth time and paying more attention to it this time #2 & #4 were switched.......