http://www.jcwhitney.com/repair/c21235j1s17.jcwx
Here a nice kit to get for your tank. As for helping get the rust out, you can ether use small link length of chain or you can use one or two large packs of BB's. Put the chain or BB's in the tank with the cap on and shacke the hell out it for a while.
awk yea the guy i got it from owns a atv slavage yard and he said he puts that in all his custom tanks he build for custon bikes. and he said he ccan get it for like 25 bucks and another guy said to buy some kind of acid and itill clean it up like a brand new one. and demon i tryed that with a few gravles thats what my uncle told me to do use a hand full of gravel and shake the hell out of it.