This was reinforced when a package arrived at my doorstep.
A look inside the box reveals a great starting point for conversion into era appropriate motive power that was first discussed in a post from June 2014.
As the box said and the pilots/couplers tell you, it is three-rail OW5, but the package came with replacement pilots and the rest (couplers & trucks) would've already been replaced anyway.
By the way, my birthday is in July. :-) Thanks, bro.