Fuel Line Connector Dimensions

Well heck, went to hit the road and smelled gas! So the ITT connectors, both feed and return were rotted out as well as the tubing on the sending unit. So the straps were bad on the tank were morto too so I dropped the tank, replaced the sender/pump and straps. Amazon has a Spectra model that comes with the pump for about the price locally of one without. SP127B1H is the number. My old pump still worked, too well. I left 5 gallons driving back home 6 miles!
  So I swapped out the supply line that goes between the tank to the filter too. I had a nice one on a parts car.
  The return line fitting was bad also. So I bought a repair nylon line and nylon to nylon coupling. These lines were not supposedly repairable, but being the return line figured I could get away with it.
  No one in my area, repair shop or auto repair has the tool to press a fitting into a line like OEM. Heating a nylon line to make it pliable did not appeal as heating nylon reduces it's memory, to try to return to it's original form sealing the connection.
  So I used a brass nylon to nylon coupling. The line actually slides over a brass tube, and then is locked in place with a nylon ferule. Nice and snug. So I replaced the end and about 6 inches of line with a repair connector.
  Being metric, the fuel lines and connectors are Supply 3/8" connector to 10 mm nylon line. Close to 3/8" but not exactly. So on the supply side if possible a repair connector line should probably be 3/8 by 10 mm.  Then a 10 mm brass nylon to nylon coupling could be used. Now 3/8" could probably be used, but under pressure 10 mm would be preferable.
  The return line connector was originally 5/16ths by 8 mm tube. The 5/16ths line and coupling are a shade smaller tubing than the 8 mm line but the 8 mm line will still slide into the 5/16ths nut and ferule and is a little snug on the brass tube it slips over in the connector. That is what I used. By the time you tighten the nut on the connector I do not see any way it can come loose.
  Now when dealing with tapered or compression ferule fittings DO NOT use teflon tape as it can prevent the ferule or flair from seating correctly. Most plumbers even use it on natural gas or propane connectors used in construction but should not.
  Dorman aka Need a Part make them. Napa had 'em in stock, Yea!!! I downloaded their OEM Solutions Catalog on line, you can then order the sku's on Amazon. Easy Squeezy.
So 800-058 is the 3/8 connector to 3/8 line for supply. 800-057 is the 5/16 connector to 5/16 nylon line. both have 18 inches of line on the fitting.
800-148.5 is the 3/8 nylon to nylon coupling, and 800-147.5 is the 5/16ths. These are the SAE non metric parts. The connectors come with an insert barbed coupling. With Dorman's tool to press it into the lines cold they would probably be fine. The tool alone is around 80 bucks. Not a lot for a shop tool, but no one has one around here has one.
  Ideally a  barbed connector could be cold pressed with Dorman's tool, especially if you have enough clean tube to attach it too.  So 800-082 for supply, 3/8ths and 800-080 is the 5/16ths. These are connectors without tubes, and only used with enough existing line to cut off old connectors and press in new ones on your existing fuel lines. The SAE sizes are a shade smaller than metric, .95  (3/8ths) and .79 mm (5/16ths) respectively.  So I hope this helps someone else with rusted connectors at the sender.

The Napa part for the 3/8 connector nylon to nylon is a 730-5644.