I finally need new tires for my old Ford F-350. It’s been about 15 years. Currently I am running 35 12.50 16.5 BFG Mud terrains on Outlaw II rims. I obviously need to buy new rims because tires are no longer made which sucks. I want to go a little smaller this time for better towing power and economy. Something around 33”. I want to keep the same vintage wheel style as well. I’m getting ready to order wheels and don’t know whether to go 17” or18”. What would the RME experts recommend? Also tire sizes, I am not to familiar with metric sizing.