Congrats on owning the finest shotgun ever made. I didn't keep up with Brownings when they stopped producing the round knob, long tang versions. Browning almost went under after mistakenly purchasing (Saltwood) walnut. Yikes! Ruined a lot of beautiful shotguns.
That wood ruined a lot of fine Safari rifles too. Yes, I am trying to fit it to a 50's vintage gun and I believe this stock is off a much later one. I had assumed they were interchangable.