Manufacturers often make changes during the production life of a gun model. Sometimes these are announced with a dash number as S&W does, or a Generation name or some other identifier (new model, etc) but sometimes minor dimensional changes in parts are not announced, though they usually become fairly common knowledge in the gun community after a bit.
the first and biggest point is DO NOTHING PERMANENT TO THE GUN!!!
Swapping parts (mag catch) is one thing, and can be undone if desired, but DO NOT cut, file, grind, stone or anything else to the original gun.
IF some modification is needed to get the new (I assume new) S&W mags to work in your early model 41, you should modify the magazines, NOT the gun.
A thought, what does the packaging on your new mags say??
I'd suggest calling S&W and talking to some of their tech people, not just the receptionist.
There are some guns where only the original mags will work. IF you are in that situation, spend what is needed to get the original pattern mags.
If you can mod new mags to get them to lock in and work, fine but don't change the gun. Fit the parts to the gun, not the gun to the parts is a good rule to follow.
M41s are great guns, long regarded as the Cadillac of .22 semi auto pistols. Friend of mine has one, I've shot it, tis amazing. Gripping it is almost like putting on a glove, and he has a electronic sight seems like you have to deliberately work at it to miss.
It is, however still a .22 semi auto pistol, which are the most picky guns I know. Don't expect ALL .22LR ammo to run in the gun. Find what it likes, and what it tolerates and use only that. Not easy with today's shortages I know, but being picky seems to be the nature of the beast.
Good Luck, and enjoy!