There are several ways to raise the FW to fit the truck. The best is to add a subframe, made from square tubing. They do make blocks to go under the trailer springs, but I would not go more than an inch or two, using this method. You may be able to change FW tire/wheel size if you have enough wheel well clearance. There is a correct track system that will raise the trailer also.
IMO, it does not matter all that much to be a little nose high. I would say 2 inches or less.
Another thing to consider with the taller tires on the truck, is gearing. Even though the tall tires only raise the truck an inch, they can change your overall gearing from 3.73, to closer to 3.55. For towing purposes you'd be better off with the 4.10 ratio.
Jerry
