I think I would mount the old PS on the new tank and make them independent. "They are likely" to start at different times, reducing starting surge / load. And of course you can adjust on / the other to make that so. You would also need whatever is used for the unloader. Depending on what that "is" it might be easy, or not. You could also make a "mini tank" on the old setup let's say, a length of something like 1" pipe, capped, with a reducing tee or even fittings welded in........give you a place to mount the switch and unloader. Remember, tho.........the air coming out of that thing is HOT just like the head. You'd likely need some sort of high temp stuff to jumper to the new tank, or else permanently mount both so you can use a copper tube.
