1941 Pickup door hinge "backing plates"

[Jmelcock]

My body man gave me a real scare earlier this week when he told me I needed all new door hinges for my 41 pickup cab! Fortunately, that is not the case. He later called to tell me that we need a square steel piece with 3 holes that goes inside of the door posts. He called them "backing plates." He sated that the piece is needed to align the doors. Does anyone know what these are called, and where I can get them? I'm a newbie at this. Any help is appreciated.