55 and 56 passenger cars had a different bearing size and a narrow crown gear.
57 and 58 passenger car had the same width housings and axles. In 1959 things got wider but the centre sections will fit up till 1964 from the passenger cars.
I have a 1964 centre with 3.08s in my 57. If you are going from non posi to posi you may have to shorten an axle about 1/8th or1/4 of an inch, just a little off of the inside so it doesn't hit the centre pin in the carrier.
So the 55 and 56 can go in the newer housing but not the 64 into the 55 , I know, I got into that mess in 1974.
Also the Corvette housing had the spring perches welded to the housing at a different angle than the passenger car. (58 chevies were coil sprung)
Any problems drop me a line.
Bob