[zac]

Probably a choke issue. Loosen the 3 screws on the choke cover and rotate it a bit clockwise 1/8 of a turn or so, and see if it helps. Your choke may be labelled so that you are turning it toward "lean" or "leaner". Not all are marked. This should help you get it off the fast idle cam. The fast idle cam has three steps. I am posting a picture of the fast idle cam lever or "follower" behind the choke housing. It is more or less straight up when you start on full choke, as pictured. On the second step it drops part way down, forward on the carb. On the third step you are technically all the way off the fast idle cam and the follower drops all the way down forward. In your case you may be able to push the lever forward off the highest step with your finger or a screw driver until you get the choke adjusted.

Getting the choke adjusted is a trial and error procedure these days, unfortunately. There is a technically "correct" way to do it, but the fact that you bought a reman carb for "your truck" only means that it should bolt on and the linkage should hook up. There were a huge number of variations of these carbs and anything you get now is just a pretty rough approximation of what is supposed to be on your vehicle. You need to have the choke set so that the blade closes all the way when you set the choke, but it needs to not be set too rich so that you can get it all the way off fast idle so that the driver's side linkage is touching the back of the curb idle screw, as pictured. The tick mark on the choke cover may or may not be in the range of the little index bumps on the choke housing. The line may end up all the way left or right of them when you are finally set, but at least it gives you a reference. Once you get this ballparked you should move on the idle mixture setting.