Ok so I found a trailer for my boat. Picked it up yesterday.
The rough dimensions are pretty close to what I needed, and luckily every part of this rig is adjustable, tongue length, winch position, axle position, etc.
So after I removed the rollers I think this will work pretty well. I can custom fit my bunks to the boat and get a rear roller on there (probably fabricated from some of the parts I removed).
13" wheels, bearing buddies, heavy duty winch, new lights and a spare rim.
Here are a few pics before and after I unbolted all the rollers and brackets.