You don't need to weld a bung onto the tank. Just make up an adapter to screw the check valve into and use plumbing fittings on either side to go from 1/4" barb fitting on one side to another 1/4" barb fitting on the other, then run it to a "T" in the fuel line between the shut-off/res. valve and the pump. Sometimes those check valves can back-leak slowly, and if you use your fuel shut-off valve on the tank, that will also help prevent any backflow through the check valve if it should leak.
I HIGHLY recommend that you have the ZN1300 supplement manual if you don't already have one. Chapter 3 goes into the deep details of the fuel system and troubleshooting. It will also show you all of the other input items to the DFI controller. It gives you several warnings about testing these injectors, too. NEVER shoot 12v straight to an injector! It can kill it, just like a flash bulb. Needs a 7w bulb in series with it to limit the current.