Popkorn - I used an 18 gal tank from an first gen camaro behind the rear axle of my 54. The same would work for your 59. Another option if you want longer legs (more gallons) is to use a 69-70 Mustang tank (20 gal) which can be had off ebay for less than $150 complete with sending unit. You might have to ohm down the sending unit so your guage reads correctly but that is easy to do.
Other options depend on how you have routed your exhaust but the side tank from a 73-up half ton Chevy can be made to work also.
Go Astros! Hope you get another chance to wear the "SHIRT".
