Thanks everyone, I won't say it was a fun project cuz it is a trailer!!
H20 I know what you mean about finding a decent tandem very hard to find, that's why when both of these came up I grabbed them. I guess we will see what the market bears on a shiny looking one.
GAB, the box is called the engager, all trailers with a GVW of over 3 thousand pounds here have to have one in case the trailer parts company with the tow vehicle, the box has a charge circuit and small 12 volt gel-cell that actuates the electric brakes ( most expensive item for the rebuild)
After selling the stereo, motor, and out drive from the donor the trailer cost me $110. I invested another $280 in supplies and a whack of labor, time will tell.