Need some help!

[Loganbpilger]

So I have a 1980 siverado long box, all original 350 with th350 and a 12 bolt rear with 4:11 gears. So far I have done a tune up, replaced the rad with a dual core HD rad, and just recently I replaced The 4brl quadra jet carb with the same number and model that is new rebuilt, It seems that i now run rougher than hell and i set it to run as lean as i could then the other day, i started it up , in +2c weather and it started missing and would not burn the fuel. I am taking the whole day to freshen up the tune up but if anyone has had this happen or have any idea that could help, it would be much appreciated.