Be careful throwing the term "split rim" around...
There was a true "split rim" 20" wheel used on trucks on the '50s & '60s that was in two halves, separating im the middle of the rim gutter.
I'm pretty sure these have been outlawed by the US Department of Transportation, about 20 years ago. Reputable tire shops are supposed to confiscate them ( at least that's the story I've gotten in Pennsylvania).
Allegedly, there were enough problems with these rims coming apart on the road, and causing injury that they have been banned.
Try to find the rims with the removeable side ring: these are usually three-piece: Rim, side ring, and locking-ring.
If it looks like it comes apart in the center of the rim, stay away from it.
Lots of folks refer to any multi-piece rim as a "split-rim", but that's not necessarily true...
There may also have been split rims in 18", 19.5", and perhaps 22" .
Good luck - I found one "split-rim" widow-maker on my '55 dump truck; it is being replaced by a regular 3-piece rim.
