Venting a gas tank

[custom10nut]

In the future, when I finally get around to taking my gas tank out of the cab and installing a steel Blazer tank under the bed, do they come with a vent on the tank? Or will I have to fabricate a vent tube myself? The reason for the question is that the filler door and filler tube I mean to install is from a late 80s truck, and the cap is not vented.
I'm glad I had this epiphany one day when I was sorting through all the parts I have collected for future project. I have a '70, and of course it has the vented cap system.
I'm hoping, with the numbers that have relocated their tanks, someone can give me some pointers.
In addition, I'm assuming that there needs to be a short length of flexible fuel line from the tank to the hard line that follows the frame. Am I right?

[custom10nut]

An additional thought.
If venting the tank is not possible, for safety reasons, are there any makers of Vented caps for the filler setup I have?

[custom10nut]

Any thoughts? I know it was late when I posted it

[custom10nut]

I think I have it figured out. I'm going to tap into the filler neck vent an then run a vent tube to a small canister set up, to prevent any debris from getting in.thanks for everyone's input.

[dmjlambert]

I would probably attach a check valve at the vent port of the tank and run a short hose to a breather or filter element, to allow air into the tank as gasoline was being consumed.

[custom10nut]

Thanks, I hadn't thought of doing it that way

[custom10nut]

Thanks, I hadn't thought of doing it that way