Borrowed a transmission jack... went out to start the truck to move it closer to the garage, and it barely cranked over, not fast enough to fire! It's only been sitting for a week and a half.
So either the two-year-old batteries were ruined by the previous owner from excessive cranking rather than fix the air intrusion, or there's a standby drain (glovebox light is my first suspect since there was no bulb in the socket, but it sure looked like it was going off with the door shut).
It won't be hard to find on this relatively simple truck, but it's still annoying. 10 amp charger hooked up for now.
Edit: The battery drain was trivial to find... sure enough, it was the glovebox light. Since today was overcast I could see it shining through the crack as soon as I looked in the cab. Just had to reposition and tighten the screw holding the switch/light assembly. It may have been "rigged"... the speed nut is there, and the slender plastic pin to keep it from rotating out of position, but there is no hole for the pin to engage.
But it's still gray and 40F... going down below freezing tonight again. Allegedly 60F for a high tomorrow. Maybe I will feel like getting underneath and wrestling the 72 lb transfer case out then!