I have a '94 c/t with 175 hp injectors, tst throttle plate and a Schwitzer turbo 285hp, with 300k miles 3500 regular cab, I have p215s and I'm thinking of going to p225s because of availability as I travel, I am pulling a 2005 HR Presidential 5er 36 ft Quad slide GVWR 16,500, hitch weight is...