The original rims on the truck would not have been split rims. They would be 8 lug in either 17.5" or 19.5". Tubeless tires will work on either, although many of the original bias ply tires either required tubes or had them added after a repair.
I have used both sizes. I could not find radials in the 17.5" size, just bias ply. Specialty Tires of America manufactures this size in a highway tread and a lugged tread.
19.5" are available as radials from many sources because they are a relatively common size for RV's and commercial trucks.
If you want to stay original, the 17.5" rims can still be found with some looking. The 19.5" ones are VERY hard to find.
The above tires are all expensive and choices are limited. If originality is not important, you can save money and have more choices by going with non-original rims.
One thing to keep in mind. These trucks are geared very low, hence a low top end. If you are buying replacement rims anyway, the larger you can go (even 18" versus 17") to get a larger tire profile will give you better top end if that is important to you.
Maybellene
