IT sucks to say but it kind of sounds like the fuel pump is gone out.

 

If each tank has it's own pump, then yes it might be.

 

I figured both tanks have a low pressure pump then there is the traditional frame pump later down the lines.

 

I traced the lines and dont see any pumps except the internal tank ones.... guess its time to drop the tank

 

I guess thats about all you can do. I don't know too much on dual tank systems but it just sounds like a pump.

 

Willyd88,
I see you're Otis Orchards. I'm in Otis also, over by the old Deans Market. Is your 74 a small block or big block FE? 6 degrees advance timing should be a good place to start (vacuum disconnected and plugged, of coarse). I'm sure the 26 deg. you found on the net is for full vacuum advance (full curve).

If your 97 fuel tanks are OEM/electrically switched on the dash, you should have a solenoid valve that switches tank flow, that functions in sync with the fuel pumps. If you've checked the fuse, and replaced the switch, that's the first part. Solenoid and fuel pump would be next in line to check.