No not off the outputs of the valve, but you can break the return line and make that the BH loop.
You will need to make it so you can loop the two together when you do not have the BH on.
And because the BT603 uses three lines you need to add a return to this spot.
If you have a loader it's already has a line attached there, you will need to tee that line.
If you don't need two aux rear controlled ports there are much easier and cheaper ways to add a BH loop.