Your easiest solution is to have the chokes reamed to what you want. There is most probably enough metal at the muzzles to do that. I cannot imagine a set of barrels that are originally choked mod. and full that wouldn't have enough thickness (at the muzzles) to open them to IC and Mod. There may, or may not, be enough thickness to have screw-ins installed. The barrel man that you are considering using to do the job can determine that. Briley thin-wall chokes can be installed by them (Briley) when other brands cannot. I have a Perazzi MX-8 that had muzzles so close together that, when I had Briley thread them for thin-walls, I had to have the O.D. of the extended choke tubes ground down to keep them from hitting each other. I can't screw both out at the same time now, or they will bind against each other, due to barrel convergence.
I have had chokes reamed out, and have had barrels threaded for choke tubes, and really think that in most instances reaming the fixed chokes to what you want is the best, and certainly is the simplest and cheapest, recourse.
SRH
