I have a '50 F47 and I've already tried removing the screws that hold the door hinges on. They will not come out. Should I keep trying or has anyone left their doors on for painting?
BTW, the cab is removed from the frame and completely stripped.

 

Leave the doors on. There will be other, real challenges to overcome. No need to flail away any longer on this one.

 

Heat, heat and more heat. When the bolt expands, you'll simply break the chemical bond that has been created by corrosion between the bolt itself and the welded-in nut on the door frame. Heat the snot out of the bolt head with a map gas torch. Let it cool a bit and then give it a try. Remember the bolts are slightly more malleable when hot, so don't put too much strain on them when hot. Also remember that the heat will transfer through your ratchet. wear gloves. There wasn't a single bolt that didn't come off of my truck when I applied heat.

Personally, I like to have the doors off for painting. Makes for getting the door jambs easier.

 

When I tried removing the hinge screws on my 1950, I tried PB blaster, heat with mapp gas, hand held impact driver, no luck. My last resort was I took my 1/2" air impact gun and put a regulator inline by the gun and turned the pressure down. I squeezed the trigger and let it slowly impact on the screws and low and behold they all came loose. I used a adapter so I could use the phillips from my hand held impact driver.

 

I left my doors on...the painter did a great job on it...