Zgator, Just kind of browsing photos since I've only been a sort of active participant at the site here for a couple of months. I see Squeakie resonded to you here, he's about the best sourse of info. you're ever gonna find over here, especially on anything Mopar or AMC high performance, others too.
I see you never really got your question on the gas tank answered yet and as a bit of a mopar expert myself, I can tell you in needs to be natural steel color. I have seen some with undercoating oversprayed onto parts of them, even all over them, but your theme here appears to be the lightweight street racer, NMCA type stock appearing drag car. So, no undercoating. I Usually use regular Testors silver spray can enamel, sprayed into the can lid and brushed on with a wide brush. If you just pay close attention to coverage and even strokes, it wont have streaks, honest, its very easy. Then I'll use a slightly contrasting color like Testors steel on the two straps that hold the tank in place.
Besides it being easy, why do I use this unusual sounding technique on gas tanks? Because the silver from the can dries, unlike any Testors bottled silver enamel paints which never ever dry, they are always tacky no matter how many years go by, even worsening over time!
Other alternatives are of course the various metalizers on the market, but they sometimes rub off even when dry requiring a clear sealer which yields less that a realistic sheen. I'd recommend by technique above, especially since you may have already completed the car. Since it involves simple brush painting, it can still be done.
Hope this still helps.
Dave B.