51 cab prep doors before removing
 

From what I see and hear theres no prep before removing the door/hinges as they are not ajustable like 55-say 70 cars as you can drill a smal pilot hole in the hinge before removing to help align or reference the remounting of the door/hinges. I have welded in cross bracing where any floor pan or structual bracing might need replacing later so the door pillar/jams,sheet metal will stay rigid. As most have posted the hinge pin or slight bending hinge plate is about the only adjustment that can be made to help adjustment. My doors gaps are fine and doors open and close great. Just want to keep them that way when I go to reinstall them

Re: 51 cab prep doors before removing
 

I helped a buddy with his '54 and we drilled and pinned his hinges. they fit well after. if you have hinges that fit well but are worn out just rebush and repin them for best results.
cross bracing before removing a big piece is always a great idea

Re: 51 cab prep doors before removing
 

I'd definitely mark them or drill them so you can get things back to where they are now. When it came to re-hanging my doors I was looking at a collection of several different hinges all in one box, there was a lot of time and fiddling to get things aligned and I am not that fussy about perfect fits.
Bending those hinges is no simple task, you are either going to be taking that door off time and again or using some serious force on the door.

Re: 51 cab prep doors before removing
 

The drilling the holes after you have the doors perfectly aligned so you can use a pin to get them lined back up just as perfect is one of those things they didn't tell us around 1980 when I had my truck down to the bare frame and subframed it, changed the rear suspenson and chopped the cab. I very honestly chopped the cab with it sitting on 4 jack stands in the shop with no bracing at all. Getting the doors alinged afterwards was a real fight.

The getting the doors sqared up before you do any bodywork, welding or patch panel replacement and bracing it up solid before welding on it is something we never thought of 40 years ago or those who did didn't share it. Simple things that don't take long to do and usually don't cost much money or any money but make your project come out so much better with far less hassles. Drilling the 4 holes probably takes less than fifteen minutes start to finish but saves hours of fighting with it after the body work and paint work is done. Slide the doors on the hinges screw the hinge bolts in loosely push the pins in and tighten the bolts.