I put the tank in the cab for a couple reasons;
Less rust-scratching, salt, and just plain dirt sitting around and on the tank.
No need for a skid plate
No need for baffling or pads to put fuel where it needs to be. The thing sloshes side to side a bit if driving the truck stupid. But forward to back there is no effect full throttle or emergency stopping. Generally the sloshing is not noticeable if driving normal. With the radio on you cant hear it.
But the big 3 were
I want to run fender well exhaust and those saddle tanks where where the pipes are going.
I have some side to side sloshing when driving stupid. But for the most part it is not that bad.
Front to rear is where the in cab tank shines. I can mash the gas or slam on the brakes and my fuel needle barley moves. No "bobbing" 1/4 a tank until it settles or risking running dry requiring pads, baffles, or special pickups.
I did not want any tank that would require skid plates or be at risk of being punctured. Also less rust having the thing in the cab which matters in Michigan.
Kind of fun to have nothing below the frame rails to worry about.
Back to the vent I rummaged around and found some bits in a tool box put them together and made this.
Nothing more then a pcv valve Going to use 2 of them. Both mounted vertical.
One will just be the pcv valve with a hose at the
top going into the tank. When the thing is running this will allow air to be drawn into the tank. But it will not allow pressure out.
The 2nd one will use the brass valve and hose. I will run a T barb from the tank with the Top of the T going to the to the
bottom of that brass fitting. When the tank has enough pressure to unseat that spring(guessing around 3psi) it will push up on the pcv's spring releasing vapor briefly into the "new" upper line do a loop above the tank and go down through the floor below the tank venting to the atmosphere.
Now that 2nd one is just to prevent a buildup of pressure in the tank in excess of say 3psi. But below 3psi the vapor remain in the tank till the purge valve opens. Then it will be pulled through the t up the current vent line above the tank do a 180 going below the tank and go to the purge valve.