You have a couple choices. For a more boxstock look try QuickSlicks CB32

Fit well, but I would glue them. Remove the wheel assembly, coat with nail polish, install the tire and roll it on a flat surface.
This is what I have on mine.

Paul Gage 19105's. These are lower profile. It allows the guide to sit in the slot better without the need for any aftermarket guide adapters.
You can use 19125, but at 12 wide you will have to trim the inside edge of the tire off (easily done) to avoid rubbing the chassis. I also advise gluing as described above.