340 help!

I have what I believe is a late 60s 340 with a holly 750 carb stuffed into a 1967 barracuda fastback that I'm trying to bring to life for the first time this year. Was rebuilt last season drove all year and put it away for winter. I started it once halfway through winter (which was tough because it was cold outside) but once running ran good. Now comes spring and I go out to start it and all that happens is a cough sometimes out the exhaust but mostly through the carb and will sometimes catch fire. It will sound like it's trying to fire then all of a sudden backfire through the carb. Timing was fine before and hasn't changed so I wouldn't think that was an issue. I even tried to warm up the intake and carb with a light and poured a small amount of gas into the carbs primarys and still no go. Checked the plugs and seemed a bit wet so I dried them all off and still nothing. Can anyone please help???