I'm about at the same spot as you on my '51.
I found Steele's website incredibly confusing, mostly because I've not done this before and not really sure what's what. I really wish they simply said "If you're doing the doors, order this kit." They have kits (not complete, you need a few different kits to do a cab), and sets of individual parts. Getting everything you need without duplicates is daunting.
To cover door windows, I ended up ordering a "Belt/Weatherstrip/Window Channel" kit from RockAuto, it's "Fairchild" brand, $130. Should be here next week, so I can't speak to quality or fit yet.
The PN I ordered was KG10288, but it's for '51-up (with Vent Windows). I'm sure they would have something similar for your '50.
Waiting on windshield, back corner, and rear window gaskets until I get doors completed and hung; and plan to use Steele for those.
I also plan to order Steele for the door rubber so I don't get into the closing issues; but their "windlace" is black (not original) so I haven't made up my mind about that yet.