1976 Chevrolet C20 Scottsdale

1976 Chevy Scottsdale C20 truck. Rebuilt CH 350LOIS engine was put in in 1998 and the transmission was rebuilt then too. Used as a farm truck so few miles have been put on since the rebuild. A new starter and fuel pump was put on less than two years ago.
The pickup will need to be trailer-ed as it is not running do to a fuel issue. It does start when fuel is put in carburetor, but doesn't stay running so we figure something is wrong with the line or the switch between the duel fuel tanks. There is rust on the bed and normal ware and tare of a well worked farm truck.