I don't know if this was mentioned but the bbd 2 bbls had a habit of warping. Might be getting a mild vacuum leak, the fix is check the mating surfaces if you find the top or base plate is warped you can heat it in an oven and then straighten it out on a known flat surface. Might need a tad bit of file work but be careful.
I always liked those carbs and still have several. Very easy to rebuild and they work fine for thier intended purpose. The 4 bbl will porbably make you happier once dialed in. Of course this might lead to a whole other can of worms, finding kick down linkage and such.
Still think a 318 in a Chrysler is weird, but I am sure they pulled the big block and still wanted to sell the car. Porbably had the 318 laying around. Glad it turned into a good deal for ya