This is a used Treadle-Vac power brake booster mounting plate/steering column pass through plate taken off of a 1957 Pontiac 4 door Chieftain sedan.  The interchange I found shows it will fit the '57 Pontiacs that came with power brakes.  I think the ones that had manual brakes had a slightly different plate.  As you can see in the pictures, this one needs to be sandblasted and some rust repaired before either painting or powder coating.  It has some rust through on an area around the outer rim - see pictures #3 & #4 for close ups.  For a show car, you would want to weld some metal into that area and grind smooth.  But, it would be in a hard area to see if you don't want to do that.  I'm sure it will have some rust pitting after sandblasting that will need to be filled as well.  Note: I currently have the Treadle-Vac power brake booster that was bolted to this for sell in a separate auction - see my other items.  Please contact me if you have any questions and thanks for looking.