Look for these number between the fuel pump and starter, they signify a late model full pressure 261.
3739365
3769717
1953 Chevrolet 3100261 cu inch, sm420, 3.55 rear, torque tube still,omaha orange, still 6 volt, RPO green glass, side carrier spare, all done
In the DITY GalleryVideo of the 261 running1964 GMC 1000305 Big Block V6, sm420, the next cab off restoration