rough idle and low rpm 351m

[offrdf150]

i have a 79 bronco with a 351m i recently purchused that ast for 3 years. it runs but idles rough and is shaky when first takeing off but clears up at about 1200 rpm and seems to run fine at higher rpms and is freeway driveable. I have replaced the ign module pickup coil coil and a full tune up , and rebuilt the carb. the timeing is set right it doesn't smoke ar make any noise confused and need any help

 

[89Bronco58]

most likely a vaccume leak or your air idle screws are adjusted wrong, what cfm and type of carburator are you running?