What size aluminum wire to feed 125 Amps 220 volt a distance of 175' and what size ground?

A 3/0 aluminum conductor will limit the voltage drop to3% or less when supplying 125 amps for 175 feet on a 220 volt system.

If the 125 amp load is a sub distribution panel that is not going to be fully loaded to 125 amps then using the exact connected load, which might be smaller than 125 amps will effect the wire sizing. The grounding conductor for that size distribution panel is #6 bare copper.