Here's what I would do if I were picking up a used trailer with unknowns -- I'd go to Wally and buy both sizes of hitch balls -- Based on what I had on my tow vehicle for trailer light
wiring, I'd buy the adapters to change my TV to the three standard Scamp
connectors (Flat4, Bargman/Pollock7 and the Round 6-pin), plus I'd also get one of those kits with a set of lights
and a long wiring harness, intended for use on boat trailers.
I'd leave all the stuf in the orig packaging and save the receipts so that I could return the stuf that I didn't use.
BTW, anyone getting one of those new receiver ball mount bars made by Reese with the impression inside to hold the ball while tightening should also check to see if the hitch balls they have will fit without a washer (on a long ball shank, the threads may stop too soon because the ball base may drop down into the bar unless it is one of the new Reese ball mounts intended for the purpose.
BTW, altho the new 13' has the higher headroom, that also means that it is even less likely to fit into low garages -- My researches show that a Scamp 13' is maybe the lowest non-folding camping trailer available, except some of the actual teardrop trailers (not the T@B, however).