I doubt you even have the dangerous type of "split rim"
More than likely you have three piece lock ring wheels, which are safe if in good shape and assembled with care.

Check out this Tech Tip http://www.stovebolt.com/techtips/wheels/
click the links for pictures of different lock ring and split rim wheel types.

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-