Im assuming you have a stock old RV 454 engine you are asking about only because you didnt list any performance 'enhancing' goodies to consider in your question....
With that said you can probably get away with putting any of the chinese $79 1.25" primary tube header kits available out there from any of the ebay providers.
BUT - if you want that motor to really breath and give you the performance a tuned header system should give you then you should open it up and find a good header that has the right size primary for your mods. The shorty headers and mid lengths are for a single purpose and they rob BB's of horsepower, nuff said. I wouldnt put anything less than 1 7/8" primary on a 454 to begin with, no matter what type head you have. These are readily available. If you want to go 2" primary then you have a bit less to chose from. But Patriot is a brand that has them in 2".
2 1/8" and 2 1/4" are typically custom but check out Mad Dog and Mikes
http://maddogheaders.net/products/chevy
http://www.mikesfabshop.com/header-sizing.html
Good luck to ya.