I wanna install this scope rail
Link

on an SLR 105A1



is it possible? if so how hard? any gunsmiths that would do the operation for a good price?

drill holes.....rivet.......any smith could do it, if they are experienced with AKs and know the positioning

All it needs to be is parallel with the top rail.  I did one on my Bulgarian project.  Install rear rivet, but not fully compressed, I squared it with a small carpenters square.  Mark front rivet location and drill.  Rivet front, drill and rivet center hole.  Finnish compressing rear rivet.  First 3 shots with my Kobra were 3" right, 3" low.  Got it zeroed in 12 shots.  The whole project intimidated me at first, was not so bad.  NOTE the rear rivet that goes through the rail and rear block need to be longer than the normal ones.