My truck is about the same setup: 216, no oil filter, not road legal, but runs. I use the standard oil off the shelf, 10W-30. There are a lot of comment threads about engine oils, but since you'll probably be changing it again in spring before any leisure drives, a modern multi-viscosity oil should do for your winter truck warm-ups. If it regularly gets terribly cold (like below 0°F), you could even use 5W-30.
