I would not use it. The material used for the cam in the early motors was different then the later cast cam, steel I think. So the early gears are made of a different material and eat up the gear on the later cast cam. Also uses different point, rotor and cap. I would have to check my delco distributor books but the advance is likely different then the later motor specs. If you take out the cam gear in your new motor, you are pulling the motor out and apart to make repairs and replace the cam, gear and lifters. Why take that chance?
Now please don’t take the wrong, you have spent all this money rebuilding a 55 motor. Why are you cutting corners now? Go on to eBay and pick up a delco 2403 distributor. Does not matter what year as long as it is a 2403. These model distributors were introduced for the 55 model year and were used up through the last 235 in 63. They were also specified as the service replacement for the earlier pre 55 distributors.
Have the distributor rebuilt and use a correct 55-57 vacuum advance.
