Get friendly with a junk yard or two until they allow you access to the HOLLENDERS INTERCHANGE MANUAL. A good yard would consult that publication anyway.
That publication lists what other vehicles used the SAME part. I know for example that the Fairlane wagons of that time period used the same tank.
I keep hearing the complaint that all the original tanks are rusted, blah, blah, blah but few mentions that the repo tanks are not of the same steel (and usually made overseas putting people like me out of work) and won't last as long as you would expect.
There are simple methods of cleaning a lightly rusted used tank, some can be done safely at home without upsetting EPA laws. Minor holes can be sealed with "aircraft" gas tank sealers as well as products like POR "Paint over Rust" polyurethenes which are sold at auto swap meets.
Yes, I am stating that some people come into this hobby unwilling to get their hands dirty/take a few minutes to attend swap meets to find out how others handle the same problem. This may not apply to you but it does apply to others reading this. Taking care of an old car is not unlike raising kids; you have to put some effort into learning how. | 
