Grit dog and Burb man.
My Brother had a late 90's Dodge Cummins with a after market lock up. It helped but was not great at the hairpin turns. He actually gave up. He got a 36' Motorhome and won't go anywhere that it won't fit. lol
When I talk about hairpin turns I am talking about being just short of stopped going both up and down. When his Dodge came out of lock up you better get ready to be hard on your brake. Some people may have to change a diaper. :>) With out the lock up and EB you would over heat your brakes very fast.
I would be very leery of taking a 5th wheel long bed up these roads. These are sharp up/downhill turns on at least 8% grade that is much steeper in the middle of the turn. These turns are like making a u turn in a 2 lane road.