'72 Gas Filler Neck

[Dashman]

I'm at the end stages of the rebuild on my Dad's '72 K10. I was merely a boy growing up with this truck, so I don't know all of it's service details. I say these things as a prelude to my question/s.

As recall, the tank could only take 16 gallons. Yes, I've seen the specifications manual that shows 20 gallons for K10s and 21 gallons for K20 (page 3). It makes me wonder if my Dad ever had to replace the original tank, or if St. Louis ran short of the specified tanks?

I know for certain that my Dad lost the key for the locking cap, and the "mechanic's shop" had to forcibly remove it. Thereby damaging the filler neck. The locking cap on it currently does not fit well, and the gasket deteriorated long ago, so the gas would slosh out when full and in a right turn.

The damage to the filler neck isn't going to allow the proper locking cap to seal correctly. I have been unable to locate a 2" filler neck bung. Now that the truck's gas tank has been bone dry for a number of years, I could cut this neck, repair the damage, and then weld it back. ...or I could replace the tank with a Spectra GM49B (see I read here a lot, thank you BTW).