return lines are low pressure.
most guys that are faking out hyds tieing the 3pt down just simply take a 90' elbow fitting with pipe thread on one side and a hose barb on the other. they drill the hyd fill cap and tap for pipe threads.. screw the cap on, and then screw the fititng in till it lines up good for the return line, then just push the return line onto the barb. to add fluid.. all ya gott do is slip hose off and remove cap.
another option is to plumb that fitting into the cover where the hyds dipstick is... etc