Try mike livingston, he use to build all the Ellis Trailers for the last 20 yrs.
He just left and opened his own shop.
If you called Ellis the cost for a triple with disc brakes would be $6500. Use that as a bench mark when you speak with Mike. Tandom would be about $5500. That would include Rims and Tires. If you plan on putting you own rims and tires, than back that out of these numbers.
Mike has a post in this section of the v drive forum with his contact info.
There is no better trailer builder than Mike. I am sure he built your current trailer back in '83.