FWIW, I drove a vortec 454 service truck for a couple of years and it used a fair bit of oil. More than I felt a modern engine should use (this was a 98 truck in ‘03). For a tow rig, I would stick to your original thought, big block all the way. Since you already deal with ls stuff, the 8.1 seems like the best/obvious thought. Big engine built for towing, modern engine controls, mullet in a trailer park style parts availability, etc. Hook it to whatever trans you feel like and have at it.
18 Ram 2500 4x4 Big C and a 6 speed
87 Blazer on 35"s