Also consider the options for sleeving - you can make a tired 26" barreled gun into a 32" barreled gun at little cost. Thereby you have a piece that you would not be able to buy because you can't find one. So, rather than look endlessly for hen's teeth, you go and buy a gun cheaply and make it what you want in an affordable way.
For example, you want a 32" barreled 20-bore hammer gun. You will NEVER find one. But you can take a tired 26" one and sleeve it. Then when you sell it it represents something that is very hard to find. Anyone who wants one will have little else to choose from. Therefore, if done well and ticking the boxes, it will sell nicely.
The long term serviceability and safety in sleeved guns is a debate past its sell-by date. It is a NON ISSUE. Quality sleeving these days is akin to new barrels if done using modern best practice.
