Another good 6V option - the Airtex E8902. It's fuel pressure range is ideal at 2.5-4.5 psi which is right at the factory spec for the 216/235/261s, and better handled by some vintage carbs. The pump comes packaged with an inlet fuel filter, and fittings are sized for 5/16" fuel line. The E8902 has been hard to find recently - not sure if Airtex has discontinued that model, or simply a supply issue - but RockAuto has 'em.
Airtex E8902.
For vehicles that are originally 12V, or converted, Airtex E8251 has similar specs, 2.5-4.5psi fuel pressure, but does not come with a fuel filter. WIX 33046 is similar to the filter Airtex provides with its other models, has a 5/16" hose barb inlet, and works well with the pump. If a hardline install is desired, WIX has a similar filter that uses a 5/16" inverted flare inlet.
Airtex E8251 and
WIX 33046.
Alternate filter for 5/16 inverted flare inlet:
WIX 33081. Both of the WIX filters are available NAPA branded - just drop one "3" at the beginning of the part number.
The RockAuto listing for the E8251 has a pretty good video from Airtex showing the installation of the fuel pump and a three-terminal oil pressure safety switch, Airtex P/N OS75. That part cross references to NAPA P/N A0014Q, or Delphi P/N FA0004 which was used on a variety of GM products from the '70s to early '90s, including Chevy trucks, and is available at most FLAPS.
Installation Video for Fuel pump and Oil Pressure Switch.
Doug