Lesson of the day, before installing fresh used tanks ensure all vents and flow passages are clear of any obstructions.
If you don't check the passages and fill the left tank with gas and then don't have gas flow to your carb, fuel filter, petcock, or the crossover line from the left tank, then you might decide to clear the crossover line with compressed air. Even with the vent cap on loosely, gas will get all over your right tank.
The good news is that SprayMaxx 2K Clear is pretty much gas proof as advertised. I wasn't figuring on testing it so soon.
Bad news is there is still some type of crap floating around in these tanks.