I have 7542. It is a Regal BLE, with original 30" bbls w/Churchill rib, splinter fore end and 3" proofs. I call it my pigeon gun. Kirk Merrington said it was a duck gun in that configuration. Heck, Kirk worked at Churchill, so now it's my Churchill duck gun.
7542 went back to Churchill in the 80's for a 2nd set of 25" bbls with a big beaver tail fore end and 3" proofs on the short barrels. I'm not sure what in the world you'd shoot a 3" 12 at from a 25" gun.
But hey, it's cool. Is your gun proofed for 2 3/4", 3" or 2 1/2"
Joe in Charlotte