My 6745 has had the gearstick housing drilled and tapped to take a 20mm return line. This is one solution, and seams to work ok.
Otherwise the filler plug can be drillet to take the return.
As far as i can tell the only factory return is via the external curcit quickfit conections, but these are 2 way circuits so are only able to be used as a return if the external controll leaver is in the corect position. Hence i am not using them for my loader