my tank has a 1/2" npt bung on it and theres a bushing with 90* elbow threaded into it that goes to an old tapered valve that doesnt seal so the fuel pump is sucking air on one tank.  the bushing has a tube stuck to it that goes down into the bottom of the tank... the bushing and the 90* elbow are completely seized together. 

i guess its time to yank the tanks out, redo the pickup tubes and bushing... any tips?  im guessing measure some copper tube to the bottom of the tank and cut it at an angle or something... i cant really find anything on marine pickup tubes.

I have been playing around with some AN fittings and I was able to thread the inside of an AN -8 to 1/2NPT on the inside of the 1/2NPT side to 3/8NPT. It is in this picture on the far left, the blue one. So all you would need is a 3/8 NPT threaded pipe nipple from Mcmaster for the length you want and put a screen of some sort on the end of the tube. I can make 2 of them if you want. I never had an anti-siphon valve on mine. Let me know. It takes 5 minutes on the lathe. Just pay the summit price of the fittings and a few bucks shipping. Also search fuel tank pickup and you can see what I did with mine. -12AN throughout.
T.J.

 I have had many stock aluminum tanks apart and the manufactures are using aluminum threaded pipe for a pickup tubes. TIG welding them on is cool but for someone who does not have a TIG and cannot TIG them on with an air tight seal these fittings are a great alternative. I did these 2 today with stainless fittings. All you need here are stainless 3/8 NPT pipe nipple and cut to length.
T.J.
You get the idea on how this works with the brass NPT barb screwed in just for mock up.