It appears that my tank has (2) 3/8" fuel pick ups. How can I verify this as I can't see down into the tubes?

It appears that the outlets are SS or Aluminum Threaded Couplings. I can see a SS nipple threaded at the bottom of each. How do I pull these to check for both pick up lines and anti siphon valves?

I'm looking to tie them together and run a 1/2" line to my fuel pump. Seem like a logical solution to get more flow to the pump.

On my tanks the fuel pickup tube is threaded into bung welded to the tanks. Have you tried disconnecting the fuel line from it and unscrewing it?
Try the easy stuff first.
Gary

It's highly likely that there is one pickup and one return. On the tanks that I've seen, you can easily unscrew the fitting and pull it out. If it has a dip tube attached will be obvious then.

They are definately couplings welded to the tank with internal threads.

I was able to look down them with a mirror and flashlight, there is a threaded pipe at the very end of the coupling. this is the item that I need to pull out to see if there is a pick up on the end of each.

Has anyone seen this type of set up?

Lets see. Your picup tube is permanently welded to the tank? There's no chance it unscrews from a welded bung? Odd.
And there are female pipe threads inside the tube at the bottom end? I presume there are some kind of male pipe threads or it's barbed at the top of the tube to connect the fuel hose to?
And there are 2? If one is a return, it may not go to the bottom of the tank, so your twin tube idea may just suck air.
How about sticking a wire down the tube. If it sticks in the tube, there's an anti-siphon valve. If it gets to the bottom of the tank, bends and geeps going, there's none.
Gary