Thanks, Chuck!
This is the book:
...and this is the fuel shut-off valve:
Earl's 230501 Earl's Fuel Shut-Off Valves
On my car, there is a 5/8-18 union that connects the 3/8 hardline coming from the tank to the one that goes forward to the mechanical fuel pump. The union is approx under the driver's seat and along the frame rail. I intend to replace the existing union with this shut-off valve, which is 3/8 NPT, so I plan on using some AN to hardline fitting adapters and AN6 to 3/8 NPT adapters to join everything. It's actually a pretty nice little valve and well suited to my fuel system pressures. I can follow up with some pictures once I get that job finished.
- Allen.