wow a company doing so well they "want" new... that sounds like music to a bunch of us, I bet.
Part of what you do not provide us with is what we call the "load center" that being just how far out from the carriage is the center of gravity of your load, do you have to lift these bodies longways (from the front and rear) or do you move them as a sideways load (left and right sides)? while a 3500lb capacity might be fine if your load is only 48inches wide and evenly distributed, if your loads are 80 inches wide and 144 inches long and must be moved from the rear and hanging from a jib boom you will need about a 15000lb truck to handle that load.