Here are two extension rails. I'm not quite sure what camera they're for but I think the smaller one is an Agfa and the larger might be a B&J (or an Agfa as well?). I can provide more dimensions if you need them. Tape measure not included.
Asking $100 each + shipping. Make an offer if you don't think its reasonable. I'd hate to have to get a camera to put them on.
Thanks for the thought, but those aren't the right ones. Because I want a bit more extension anyway, I think just building from scratch makes bore sense for me.