doesn't take too much imagination to take the fill cap off and drill it and tap it for a fitting.
same with the side cover.
on my naa i had one of the skilled machinists here modify the blank cover so i could use a generic oc valve as a remote.
all my other tracors except 1 that have an aux hyd valves have da valves.
i do have 1 tractor with a simple diverter.. but it has SA hyd loader. I no longer have any setups that use return to tank hose like that.
I believe TOH ( that skilled machinist i spoke of ) may have pics of a return to tank cap cover he makes.