Whatever you do, DO NOT try to expand the clamp. It WILL crack. If that happens, you'll be scrounging new ones from an old frame to replace them.
Those cables look exactly like the ones I bought from RockAuto. Didn't fit, and the return window had closed.
Bought cables from another vendor - they didn't fit either, and I was able to return them.
The Stovebolters put me on to cables from LMC Truck and they fit like the originals. They have a groove in the part that goes in the clamp that the bolt goes thru.Their PN 34-3806. But mine is a '51 with Bendix Brakes. They don't list that PN as fitting a '50 3100. But it might be worth a try as they're ~$20 each.