I think the hard part would be to make the repair level. This would be important for the seal to do its job of sealing the vent at the top of the seal. It doesn't take much of a gap there to allow a bunch of water into the cab. You might want to mix up some JB weld and test it out on something that has a similar size and shaped groove and see how it works. As it hardens, try to find the sweet spot of when to try to put the finish smooth on it. I don't think you want to let it harden all the way and then try to grind it level.

1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission