Someone may come up with something but a trip to the wrecking yard with a measuring tape may be the best way. That and the filler tube location, that makes all the difference in the world. I was going to make a kit to put the 65 Mustang tank in a 58-60 Rambler American being those Rambler tanks rust out all the time and the Mustang tanks are available new. But the darn filler in in the top of the tank and to make a filler go over to the fender where it is originally it would be tough. But in your case, if you want the filler go come over to the side like I did on my truck you need a side filler location. If you are willing to have a door in your bed floor the Mustang tank would probably be a killer easy install. And Like I said they are available new. I am not talking about installing it like it was on the Mustang with a big square hole in the bed floor. Mount it below the bed with the filler going thru a small hole in the bed floor. I personally don't like this but it may work for you. Discount Body Parts - 1965 ford mustang replacement fuel tank repf670105 - 1965 Ford Mustang Replacement Fuel Tank
Here is the Nova, again, with reproduction (I hadn't thought of that!) there are tons of these older style tanks available. They even have them modified for fuel injection, very cool. With this Nova you would make a filler door in the fender as I did.
you want someone to come over and install it for free too?
you could always do a search, there is a very active 55-59 chevy truck thread on this forum
also a very active 47-59 chevy truck forum on 67-72 chevy trucks