Need Help Dont No What Else To Do

[C.20]

Hows everyone doing i got a problem with my 1971 chevy c20 350 sbc so recently after this snow storm in north carolina the truck would not turn on so me and my son did i tune up changed the cap,rotor,igniton module,spark plugs,wires the truck turned on we went down the road and all we got was horrible backfire so we thought it was the carb so we changed the carb and it still did it but it got better until u gave the truck alot of gas and it was back to backfiring i dont no what else to do if someone has some advice that will help us out a lot because its my sons daily driver!!