Vibration in 4wd front end after brake job?

[JJorgensen52]

I just did a full brake job on my truck - new drums, wheel cylinders, rubber lines - and added a power booster (had to redo most of the hard lines in the process). Bled the system out, lubed the starwheels and replaced springs, etc as needed (shoes were new about 6k ago and were fine). Truck stops GREAT now.

Problem is, I have a front end vibration between 30 and 40mph. It was really bad at first, has diminished a bit. It is not consistent - doesn't happen every time I pass that speed range, and goes away when braking.

Had to remove the hubs to do the front wheel cylinders, have double checked the adjustment and the bearings are tightened to spec with no slop.

Anyone have any ideas as to what this could be? Symptom is new since the brake work. The only thing I can think of (having eliminated the bearings) is that maybe I have an out of balance tire that was on the rear and got mounted up front? Could one of the drums have a non flat mounting surface?

For reference info:
1969 K10, front Dana 44 w/ drums and closed knuckles. 15x8 steelies with 31x10.5 BFGoodrich All Terrain TA/KOs. Tires, shocks new within 6k. Driveshafts are both new, pro balanced. NV4500 / NP241 that has probably 800 miles on the swap and no prior issues.