Polyethylene gas tank question

[chevybill]

I have a poly tank kit for my 70 lwb with a metal bed.

The fuel filler neck is only 1.5 inches outside diameter, so should there be
corresponding rubber fuel filler line at the local parts store (NAPA)?

Then how do I go from a rubber filler line to metal for a gas cap?

I am probably going with a bed floor filler, unless I find a filler kit for through the side of the bed.

Is this going to be a big problem to overcome? I have not found anything in catalogs to go from this small inlet on the tank out to a gas cap.

I looked in the FAQ section and the installs over there deal with metal tanks.

So any assistance is greatly appreciated.