A backwashing filter with a Fleck 7000 control head is my recommendation. With pH of 6.5 Calcite (only) is indicated.
I recommend at least 2 cubic ft of media and 2.5 is preferred for higher flow rates provided your well/pump can provide the required backwash rate.
Installation involves making the plumbing connections (prior to the softener) for inlet, outlet, and a drain connection. You also need an outlet for the control-Time Clock is appropriate for AN filters.
Here is one internet supplier (there are many others) so you can see a representative range of sizes/prices along with required backwash rates: