I'd kinda like to keep it - so I started looking for a replacement. Ebay turned up bronco tank valves, but not the saddle tank 3 way valve we have.
Then this popped up:


Naturally, i wanted to know more about this provider - all our saddle tanks were dealer add-ons after all - maybe this is the original source!
However, it's hard to read the face plate - but i did find this while on the Googles. In multiple years of Popular Science and Popular Mechanics these adds show up:


Note that the name changes between them... i think the first is from 72 - but the later one is from 77ish? i can't recall but theres dozens of scanned Pop mechanics pages available that can be located. Just search Waco pickup tanks popular mechanics and there they are.
I'm not sure this valve will fit the bolt holes I have, it's on the way though. The handle of the valve matches mine exactly, but i didnt not have a face plate. My tanks were the metal ones, these seem to indicate a later era with the poly tanks.
Another piece to the puzzle perhaps, or just a curious artifact from days gone by. Hopefully this helps shed some light on the kits we had available once upon a time.
EDIT:// theres also a current manufacture MAIN/AUX/OFF style valve on ebay for anyone needing them... LINK TO ONE HERE https://www.ebay.com/itm/FUEL-TANK-SELE ... 1998974470
And heres a brand new manufacture 4-way valve - main, and 2 aux tanks. https://www.ebay.com/itm/Anderson-200-S ... 4120277803
Both of these use the exact same handle as the originals did. So if you need a new valve and want the right look - this might be an option.