I do know of the Kiln gun cases and they used to be sold so much that their were swagging dies made to make them fit contemporaneity 8 bore chambers. I have a group of shotgun cases coming from the UK including 4 and 8 bore brass hulls and was probably going to get either those or modify them and get them copied at a machine shop be about 150 per case. I was also thinking of tacking a 10 gauge base and useing compressed paper to build it up at the back and make the hull tube.
Also the barrels are fine with what I have seen shiny bores no cracks or separation in the Damascus the lock up lump and forend are solid and they ring true and barrel thickness is well beyond average of 8 bores for the times, especially for 2 1/2 to 2 5/8 thick walled cartridges it passed Proof when made but safety string for the first couple rounds would be my first choice.