I have seen Folsom barrels fit to Baker Gun and Forging Co. receivers, but I don't know the amount of work required. In general the Folsom barrels will be narrower across the breech than the Baker Gun and Forging Co. breech.

I measured a couple of Folsom 16 and 20 gauges and find that the 20 gauge frame is slightly narrower at the bar and sideplates. Very small difference.