79 f150 carburetor issue??Help!

Hi, i have a 79 ford F150 with a straight 6 156,00 miles. The problem is the truck doesnt use a drop of oil but it is always blowing out black carbon on start up. Durring normal use the black smoke goes away but seems to build up inside and wont run properly after a while until i rev it out. the problem keeps getting worse and now it stalls at idle and even when im driving down the road. i have checked all vacume hoses and done a full tuneup.
My question is what could it be? Does it sound like the carburator needs rebuilt???? thats the only thing left that i can think of....I got the truck with around 100,000 and to my knowledge it has never been rebuilt.
I am thankfull for any advice that anyone can give me.
clint

Sounds like your choke is out of adjustment, follow the procedures in the shop manual on how to adjust it.