Gas tank modification?

[McCoyAZ]

Lets not debate moving the tank under the bed.

I picked up a 25 gallon Chevy Blazer tank that has the filler neck in the center rear portion of the tank and the filler spout is not vented like you see in more modern tanks.

I want to close the current filler hole and move the neck to the rear side of the tank where it would come out in the step side fender well and then add a fuel door on the back side of the step side fender.

The question is:

What size filler neck should I use and do I need to consider if it is vented or not? How did they vent the early 70's Blazer tanks?

I know we will have to cut a hole in the frame rail and then add some support, that isn't an issue.

The mod will be somewhat like what Lake Roadster did with his.