Discontinued by GM
This is the in fuel line filter as shown.. rare now but used pretty exclusively on the likes of 68-9 Corvette and Impala, Chevelle, Caprice, Biscayne, BelAir, Camaro, Nova, Monte Carlo and many Others.
These filters have 5/8-18 Thread Inlet and Outlet,
these filter have the vapor return pipe as well.
Discontinued .. but you can pick them up on US ebay every so often from around US$40 to US$ 150 or so. Carefull as their is more then a few fake ones around too.