Looks something like Simplex Criteriums or derivative on there....so it coul be a lot of Delrin parts in it, so not a big loss if you replace them. If all or most of those black parts are indeed Delrin, they look pretty dried out and crispy, so I wouldn't take a chance on them if I were you. I vote to replace them ASAP with something decent like your Suntour gear. Most Suntours will be much better for you and the bike in the long run. You can always "re-Simplex" the bike later if you want to with maybe an SX610 RD setup and maybe even clamped on retrofrictions.
Chombi