Carburetor size Question

I think it should run great . And you should be fine with 3.23 and those tall tires . Of course if your freeway drivers are like ours 70mph is crawling . I swapped 2.76s into my Barracuda and still run 3200+ rpms on the freeway . Thats with 225/70-14s though . Your truck is too heavy for 2.76s. It would be a dog .
If you go with an OD trany ( which I would since its an easy install in a truck ) I would go 3.55s or 3.91s because of the tall tires... that is assuming you need to buy gears anyway .

.74 OD = 2500 rpm running 3.55s and 28" tires