Welcome!

Read more about rim types here: http://www.stovebolt.com/techtips/wheels/
Your original rims are probably OK and safe, you may not need new ones if you don't want to.
If you do change rims to the one piece tubeless type you will need new tires to match, this entire swap can be expensive.

New rims are available from Accuride, catalog: http://www.accuridewheels.com/completeversion.pdf
You would be looking for 22.5" 6 lug Budd stud centered wheels.
Page 18, probably part number 28157.

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-