Unless you find a second one, I would not butcher the mount. Odds are that you will never own a Carl Gustav, but then again you never know.
Here are some shots of some of the various adapters used with the 1919 and the 50 cal.
Below are (from left to right) the adapter for the TVS502 to the GPMG, the adapter for the TVS 502 to the M2 50 cal, the adapter to adapt the larger rail of the TVS502 to the smaller rail of the PVS502 (the starlight usually used on the FNC1A1). The last piece is a spare of the mount that goes on the bottom of the PVS502.
Below is the angle bracket for the GPMG. It is held on to the sight base by 3 screws, and a sefety pin gets put through them to prevent the screws form loosening.
Below is the GPMG mount along with the rail adapter on a GPMG.
Below is the mount with the adapter fitted:
And lastly here are a couple shots of the GPMG fitted with the PVS502 night sight.
The sight shown was more often found on the C1A1 rifle. The actual night sight for the 50 cal was usually the PVS502, which was about the size of an ice cream pail. The sight you have was most often used with the Carl Gustav, but in the case of all these scopes, there seemed to be various adapters to allow some degree of interchange. Problem was all these adapters were B class, and rather small, so it would seem the QMs did not merely keep a bin full of them. Plus, back in those days, you had to have entitlement to hold things like these: no entitlement meant no holding it without doing a MACR, which was usually the doorway into a ravine with no bottom.
When they were getting rid of the night sights here in Shilo, I asked for the afternoon off work so I could go attend the auction. I ended up buying all but one of the available 19 sights. Within about 3 months, further sales of these were cancelled by the DND as sensitive material.
Since I bought all the sights, the auctioneer gave me a milk crate or two of the various adapters. Before anyone starts PMing me, they are all long gone, with the exception of the few pieces I kept for my collection.