Was parked.. started the truck and noticed fuel was leaking from the fill cap at the front cover. Both were filled to the max. Does each tank act separately or does one pump into the other?

 

Are you referring to your 1989 F150? If so, it could be the Dual Function Reservoir (referred to pretty often as a fuel tank selector valve), that's mounted inside the frame rail, in the area below the driver's seat.
1990 and after trucks got a different system, with check valves in the in tank pump assembly.
Do you have a Haynes manual? The process for checking the DFR is in there.
There are also threads on this forum with detailed explanations of the fuel system.

 

https://www.f150forum.com/f10/fuel-issue-549023/