A split rim divides into two pieces witha little of the center on each portion. There also are 2 piece lock ring wheels where the outer lock ring is split and locks into a groove on the outside of the wheel. then there are the 3 piece lock ring wheels, an outer ring slides doown between the tirebead and wheel and then there is a split lock ring that locks into the groove on the wheel to hold the outer ring in place. There is a fourth type which came on my 38 1.5 I haven't seen mentioned it has a solid lock ring with a oblong inner edge to lock into the lip of the wheel. On my 38 It had a mix of tires and rims. 600X20 on one side of front 650 on the other and mixed 700 and 650 on the back. If they are 20 inch rims they sould have the same diameter what may differ is the width of the wheel and the depth of the offset to keep duals from rubbing sidewalls. another possibilty since you are including lock ring is diffrent styles there. On my 54 5 wheels have one style of lock ring 6th id different though they are all the 3 piece type. maybe some one else can explain it better.

1938 1.5-Ton Chevy
1948 2-Ton Chevy

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