HV oil pumps also make better pressure at a lower rpm.
I'd use one in a tow rig, myself. You're not likely to be running high revs where a HV pump is going to be taxing the bypass or anything else strange. It'll build pressure sooner and keep pressure high at cruise revs.
Likewise, modifying the oil passages can allow greater oil flow and thus better cooling of components (especially pistons and seals) which may be a benefit in a tow rig. Those long mild grades can cause an awful lot of heat soak... I'd probably also look at a higher capacity oil pan - mostly for heat regulation as well.
