MISR-10 came in with 10 round mags and I think the narrow magwell. It can be milled out to accept a standard magazine. Not sure if a bullet guide is installed
If unaltered - $800 due to having to pay someone $200 to properly mill the magwell and make it work correctly and the $ to add the requisite USA parts once milled.
Since the magwell has been opened - check for lateral play and fit. Make sure it functions. If all good - start at$1,000 and see what he says.