need to spread the stays, but only at the portion nearest the seatpost and BB area. the dropout area is as wide as it needs to be. I need some ideas/direction.
I don't think there is a vintage cruiser frame that will accept a 26x3. Extending the dropout would be the only way. I have fit one inside a Scwhinn Heavyweight fork.
I'm putting those size flames on front and rear of my Highboy. The forks and frame extension are getting welded this week. They fit in large cruiser forks with just a little grinding of the brake mount, but I wanted it higher, so it's getting welded. The rear needs extensions, but it did fit on my old Schwinn, but the tire isn't perfect, it would barley touch the dropout if I aired it up to 40 psi. The wheel was straight, the tire wasn't. So you'll have to make room in the rear somehow, extensions may be the only way, to widen the frame may wreck it.