My '50 3100 has the slider type and is original to the truck. Or more correctly, the slider track is original to the truck, I bought repro carrier parts. The story that I have heard is the reason the original slider carrier parts are so rare is that they were a PIA to put the spare back up. So on the roadside the carrier parts and the spare got thrown in the bed, later the carrier was thrown to the edge of the driveway and later still thrown in the dump.
