As far as your gas tank , go to OSH or other " Big Box " hardware store and look in the flooring dept. for bottles of " Jasco Metal Etch " ~ it's Phosphoric Acid and you pour a few quarts into you tank (after it's out of the cab , dig) and then a few gallons of distilled water (0nly .99 CENTS @ the drug store) and then a package or two of BB's , plug the outlets and shake the beejeebers out of , let sit and shake some more , keep on shaking and rotating it untill you see shiny metal when you peer inside it , get some clean gallon jugs (water jugs from neighbor's recycle bins) and a LARGE funnel , lay some clean felt (thift store) in the funnel and strain the liquid back into the jugs , remoave the fuel gauge sender and look in there with a flashlight , if it's shiny clean , you're good to go , I usually find I need to pour the mix back in and slosh it around a few times , each time I drain it I strain it and then I discard the filthy felt scraps , you'll prolly want to pour in a couple more boxes of BB's too (I clean & re-use my BB's but hey , I'm a Yankee farm boy)
Once you've cleaned it all out , consider buying a gas tank lining kit from your local dirt bike Moto dealer , maybe _two_ kits , you'll do a better job than the radiator shop will .
Be aware that the new , re-pop fuel tanks
ALL LEAK and will need this same cleaning and then lining before you can use them but it'll go faster as they're not rusty inside . of course they're so poorly made they usualy split and leak again , leaking fuel in the cab IS NO JOKE .
I use only original fuel tanks as I watched a fellow burn to death in a car once.....