I faintly recall that type tank.
I marked up your middle picture and posted it here. You should have everything you need but the new tank. The curved light gray line goes form the injector body that contains the injector, injector throat under the injector after you remove the injector, and the injector screen/filter.
The dirty brine line goes from the brine valve to that tank.
You have a brass 2500 regenerated version control valve set up for PP.
I could sell you a new tank but I have only once sold a greensand filter and that was over 20 yrs ago. So find someone that sells PP and call them asking them to get you a complete new tank with a 5'-6' long piece of new 3/8" brine line for it. You need the brine pickup with an air check too. You should go with a safety brine valve too, a 2310 float controlled valve, that prevents overflowing of PP water if the tank overfills for some reason. They should tell you how to adjust the float, it is not used to set the volume of water in the tank, it is a safety float so it is set to close the valve before water can flow out any overflow fitting or the brine line hole in the tank.