Best place to look for gas tank and parts

I see Quanta advertized all the time in the MCG, for gas tanks. 800-235-8788 or gastanks.com. As for the sending units, they are available just about everywhere. I've seen them on ebay, both in stainless and OEM for right around $50.00 and they come with the gasket. The lock ring you can reuse, and the the tank pad you may have to reuse also, or make a new one. Good luck with your search!! Geof
Thanks Geof . . . . got a question too . . . they list a 5/16" and a 3/8" . . . How do I identify what I have? My 73 Dart is an original 318 car, but where do check to verify the size line??

Thanks Rog