It's water.
Rock the car back and forth to mix up what's in the tank, then crank over and use your fuel pump (carb side hose) to give you a sample in a clear container. Let the container sit for a bit. If you see the fluid in the container seperate, there's your problem.
Undo the hose on the tank side of the fuel pump (to disable it's ability to souce fuel from the tank) and put known-good fuel in the float bowls. Check the plugs are dry. Start the car.
You probably won't have to drain too much from the tank, the water is on the bottom.
I've done this several times since I last checked into the BB (what's it been, eight months?). I give ignition, timing, fouled plugs, etc. about a half-hour of my time before I decide it's a contaminate in the tank. Most recently on a 145E... which is weird...don't know what it was but it wasn't water, and it wouldn't burn.
Best of luck,
Shayne.