Is the trailer GVW 17,500 or the combined GVW 17,500? Either way the load is at least 9,000 more than than the rated capacity of a 3800 panel.
The 500 Cad should be plenty to make it move, but unless you re-gear the rear you're looking at spinning that low speed torque monster pretty fast moving that truck at highway speeds.
But the big worry in my mind is stopping it. That 1-ton panel is rated at 8,800 lbs if memory serves. The old style brakes aren't up to stopping that load. Sure you're going to add a brake controller and expect the trailer brakes to handle most the work, but when a wire breaks or some other failure occurs you're in trouble if your truck can't stop the load.
I'm not an expert on big trailers, but I'd expect a three-axle trailer nearly 40 feet long to be a gooseneck type. That big of trailer on a ball is going to need a class four load leveler hitch at the very least.
Don't get me wrong, I love the idea, but engineer it to work safely! Can you build it to handle this safely? Probably. Would it be the cheapest way to do this? I doubt it.
The 500 Cad is a wide motor. You'll be moving the steering box to have enough room for the motor and manifolds. Converting to power steering is probably the best answer there.
