I see you understand the suggestions and are attempting to take it to a shop along with including Father. Glad you got the truck.
I have a 55-59 GMC maintenance manual. In reading the Camber, Caster and Toe in section, Caster is the probable cause of your issue. Camber and Toe-in are related to each other. The exact issue is mentioned caused by Caster. It also says to be sure wheel bearings are properly adjusted before alignment procedures.
Issues mentioned: Worn King pins, steering knuckle bushings, bent steering knuckle or bent axle center. Also: sagging springs, uneven tightening of spring Ubolts. This is all straight out of the manual. Get a Chevy maintenance manual and read and give a copy of the alignment section to the shop.....or use it as a tool to listen and question the tech. Go over each item.
Many shops require all that stuff to be fixed before they will align. That may or may not be a money grab. It seems prudent to me. Other shops don't care, that may or may not be a money grab. They get the alignment fee, then you come back and they get the fee for replacing everything and another alignment fee. This is a either a paranoid way of looking at it or a real life way. Depends. This is why so many of us are DIY'ers. But we can't do everything so we find an honest shop. You can do all of the front end parts replacement if you have the tools and study (maintenance manual). Most of the tools are free rent at FLAPS and the parts are all available. IMO The hardest part would be the king pins. All the instructions and pictures are in the manual.
The result numbers you gave for alignment are hard to check per my manual. The camber can be given in degrees or inches, if it's inches it is wrong, if degrees seems OK (MM= 1 deg +/- 30'). If the caster is in degrees it seems OK (MM=1 deg +/- 30'). The Toe-in seems incorrect, one is at max, other is over max (MM= 1/16-3/16) 3/16= .187. Maybe total Toe-in is the savior. I don't see why total would mean anything? Spec is per wheel.
