Cold start issues

[C10longwb]

Alright guys im in the process of getting my 1970 c10 on the road and I've done alot of work to it so far. It's starting to get cold in Texas and I started my truck the other day with the new carb (btw it's a 250 sright 6 with a 2bbl Rochester w electric choke) and it ran smooth and idled great I gave it a little gas and it reved up some and it sounded a little lean.. Yesterday I started it and it reved up to (guessing no tach in truck) like 3500-4k rpm it was way up there i shut the truck off and scratched my ead and started it again and let it run this time to see if it would come down and it did start to idle down the a little hickup and a little poof of smoke out of the carb then it reved back up and it repeated that like 4-5 times before I shut it down then it gave out a big backfire I started it up again tonight and it reved up and never came back down.. Idk if it didn't get heated up but I don't like how high it revs right off the back Any suggestion would be great thanks
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