Oh Cool, so you did end with that powder coated roller? That kinda cracks me up. You paid for a roller about double what I'd pay for a truck in fair to good shape.
But, you did get a good deal for a full restoration project. I think you noy only saved money in parts, but in labor and services too and probably 6 months to a year head start on your build.
I don't have any of those pics of those set ups. Tough call really. Maybe keep the kit that's harder to sell, or the one you'll take less of loss on. For the purpose of use, I'd go with the 8inch, but for the purpose of show, and I think that's what you're building and don't know it, I'd go for the 12inch. As nice as that thing is going to be, I just don't see it getting dirty, I really don't. I think you're building a mall crawler.