D.A.T., I can't say for sure, but most if not all of the major parts I believe were unchanged. Pre war guns were hand fitted though, so a modern part that looks the same might need some hand fitting. Barrels are a good example. I have switched a couple of Belgian A-5 barrels out for the later Japanese screw-in choke barrels. Neither was a slip fit, but both ended up working fine. One gun was a Light Twelve, The other gun a Magnum 12.
I don't know if it's even possible, but never try to put a 3" chamber barrel in a standard receiver for 2 3/4" barrel.
Check online and see if the Browning repair facility at Arnold Missouri is still in business. I think it was Art's Gun Shop. They could give you detailed answers.
I've never had to change a single part in these fine shotguns. Even the springs hold up. They get shorter over the years, but still work.
Good shooting. Tom