Towing 18ft boat(3500lb load), I have an 2004 Tahoe now with a 5.3 and I don't think any less motor could comfortablel pull it. Looking at 2016 and 17s now. With 6spd trans, do you think smaller motor 4.3l could pull this rig on flat land and about 1 or 2 160miles round trips a month