Ok, so my eco swap on the sedan - this is one of the final things I need to figure out.

I junked the fuel hard lines that were on my 99 since they were rusted to high hell and would eventually rust through. I took all the hard lines off the 03 donor car I bought since they look A LOT better than the ones on my sedan. But here lies the problem. The guy I bought the car from sold the gas tank out from under me which was a dick hole move and he also cut the hard lines after the fuel filter and the return hard line before the quick connectors.

Its not a big deal but I am stuck making my own setup back there now. I want to run a better fuel filter than the stock ones and possibly do away with the @!#$ty quick connectors. I think they are different on the 00+ compared to my 99, I don't remember for sure but I know the ones on the metal 99 tank were a royal pain in the ass.

Correct me if I am wrong here.. but are these the hard line sizes?

Supply - 3/8ths
Return - 5/16ths

The Supply will be easy to deal with since 3/8th converts to a -6an fitting no problem with 3/8th tube nut and sleeve and I believe they have the quick connect fittings to connect into the GM plastic hard lines. But I've been looking through my Russell catalog and am having truble trying to figure out what to do with the 5/16ths steel return line. They don't list a 5/16ths tube nut or sleeve and I'd like to go with an -an connection over a sloppy fuel injector hose and clamps setup.

Yes, GM standard is 5/16 return, and 3/8 feed. I've been dickin with fuel pumps for the last week on my roomies project car....

Are they measured by Inside or outside diameter?

5/16th = -5an fitting if its measure by outside diameter.
3/8th = -6an fitting.

I think they're measured on the OD cody, but -AN refers to ID

the other thing is the tube nut/ sleeve fittings might not be rated for the psi we see might want to double check that.

I was going to do the same thing to adapt the hard fuel lines on the skwirl over, but once I saw in the rulebook that the fuel lines had to be opposite the bell housing, I decided to just run my own hardline.

then, I talked to the guy at jegs and he said that the hardline they had wasn't rated for efi, and that I can run straight -AN hose as long as its clamped to the body.

it sounds more expensive, but in the long run its cheaper because you wouldn't have to go nuts with adapters and crap, and way easier to deal with. The only thing you'd need to do is have a clamp every foot or so to keep the hose tucked under the car and nice n safe.

its exactly what I'm doin, -8AN for feed and -6AN for return.. the only difference is I'm putting the lines on the passenger side of the car instead of the driver side.

Well my Russell catalog I swiped from work had a technical diagram tucked away in one of the back pages...

AN size ---- Metal tube O.D.
-3an -->3/16"
-4an-->1/4"
-5an-->5/16"
-6an-->3/8"
-8an-->1/2"
-10an-->5/8"
-12an-->3/4"
-16an-->1"
-20an-->1 1/4"

I found some SS steel tube nuts and sleeves on Jegs and Summit. Pretty sure those will withstand what pressures the pump will put out and seal like automotive brake line fittings. I'll see if I can order some in at work and save a couple bucks.