FM means Argentine, right? The external ejector and roweled hammer were the standard in Argentina if memory serves.
The dinky, one sided safety was on earlier models, while the 95 had the extended ambi safety. Also, the front sight on the 95 was dovetailed, while earlier ones were integral to the slide (I think).
Given the above, I would say yours is FM 90 or earlier, not 95.
Being Argentine, it was made by license, so I would think most parts would be common. Others can answer this with more certainty than I. As I recall, the Hungarian hi powers were not made under license, and some variants weren't really hi powers.
Regarding the sights, one option is to send the slide to Novak to install them. I have read great reviews of their quality and service, with turnaround time not being terribly long.
SOMEWHERE around here I have the late Stephen A Camp's book on hi powers. He was sort of the BHP guru for a long time until his death. It is one of those spiral bound, self published books, and not something you can find on Amazon. I will hunt around for it and see if it has any recommendations.
Regarding BH Spring Solutions, I have not used them yet myself, but their kits have received hi praise in hi power circles (see what I did there LOL?) I haven't replaced any springs on my hi powers, but when I do it will be BHSS.
Hope this little bit helps ya, Johnny