I have two in my garage. One is pretty clean but will need to be stripped with very minor body work and have the inner tank sealed, and one is rougher and will need more bodywork and sealing.
72-78 NOS tanks if you can find them go for $500-$600. Nobody makes aftermarket tanks unless you purchase the polished aluminum ones out of Japan for $450 a pop. PM me your email and I'll take some pictures of what I have and you can shoot me a reasonable offer.