My '93 Spanish Mausers are .081" higher in front than the rear.
If a Farrell one piece mount were used, it is .157" difference, which means .076" of shim in the front would be needed.
For hunting rifles, I prefer two piece.
I allign them with a scope and rings while I glass bed the fit of mount to reciever. When the glass sets up, I tighten the screws.
That way I don't have to lapp the rings.