Obsa...
The "out-lawed widow-maker split-rims" ( did I leave-out any other names?) in question are the two-piece rims that separate in the center (dropped) section of the rim.
There are no locking-rings around the side flange.
The true two-piece 20-inch "split-rim" came out in the later '40s-early '50s, and stayed around through the '60s. If assembled incorrectly or worn/rusted badly, they can come apart with catastrophic results. These are the true "widow-makers". Most DOTs have banned them from use on public roads.
The term "split-rim" gets used liberally, usually applied to any multi-piece rim, 15" thru 20" ,six-lug through 10-hole.
The other ("safer") 20 inch rim found on older trucks is the three-piece, with a locking ring, then the side-ring flange, and finally the rim section itself. These are still legal, although each rim should be carefully inspected for wear/rust... if assembled incorrectly, these too can come apart when being aired-up...
Then there are the one-piece tube-less rims that came along later.
A reprint ( or original) shop or owners manual for your truck will have instructions on mounting tires on these rims...
