I run Rotella 15w-40 in my 261. I researched that as well and found several that run this grade in Stovebolt engines.
It doesn't look like your engine has an oil filter. Is there a canister mounted anywhere on the drivers side? My previous 216 did not have a filter, which was very common, so frequent oil changes might be a good idea.
If you're going to drive it, why worry with painting the frame? Just keep it out of the salt. Personally, I would clear coat the exterior, rebuild any of the brakes/front end/rear diff/steering that it would need to make it safe and reliable, and drive it!
