You should have the two-piece lock-ring style rim, not a split ring on the truck. GM used them because a farmer could break it down with a minimum of tools. While they are not that hard to break down if in good shape, I let a truck tire man do mine, he charges $5 for each time he touches it. Meaning to break down, it's $5. To mount is another $5.
There are not any good replacements, the problem comes with the tie rod on the front. Setback on newer rims is too deep, and the rim hits the tie rod end. Some guys have used trailer wheels, but then you can't use your hubcaps.
If you are going to use the rims, be sure they are cleaned up, and there isn't any major rust pitting on the lock rim or wheel where the parts mate. If there is, I recommend torching so they can't be used again.
