Stubbe, the 1346425 piston came from a 1953 322 with standard bore. The '53 piston has a very high crown compared to later years. The crown is wider on the '53 too. By reviewing the pictures in the shop manuals, the '53 piston looks like it will hit the head or the valves if used with a later year head.
Buick lowered the crown considerably for '54. It is narrower as well. They raised the crown a little for '55. Then raised it a little more for '56. The heads are also different for each year.
Buick raised the horespower a little each year. It would be good to get the serial number from the block on the spare engines to see what we are dealing with. There are more differences between the years of the 322. Hopefully you will not have to mix parts from different years to build up the spare engine.