Seam line on what? The center of the road wheels? Depends really on what you are trying to depict. A newer tank would have a slight seam there, as the rubber wheel is made in much the same way as a plastic kit is, 2 halves to the mold and injected, so there will be a seam down the middle of the tire. However on an older used vehicle, those seams wouldn't be there as they would be worn off.

A well maintained but used vehicle would actually have a mix as new and old, but since they are painted already, I would just live with it.