Weird.
If the trailer beams are a standard spacing I'd just swap a torsion axle on. "If" is a big word though sometimes.
If is the key word... which it is not...
Its likely off the shelf parts on all of those bushings, along with that leaf spring. Some measurements should be all you need at any decent trailer parts shop.
And they do.. tore into it last night and just got back from the trailer store... with the exception of the shocks everything is available.. surprisingly the bearings, races, and seals were in excellent shape considering their age, but they're getting a work over too.. The springs etc.. all in good shape, or should I say I have far worse cursing down the freeway..