You might also try to find out what the regulations are for where you are living. Some states dont require emissions on "collector" vehicles. Like here in Colorado where I live, if you have collector tags on a vehicle, once you get the original emissions for the collector tags you dont have to have emissions on the vehicle again as long as you own it and keep the plates current. I have a 72 and have not had to emissions the thing since '97. Here, any vehicle over 25 years old is qualified to get the collector tags, but if I decide to sell the thing then whomever buys it will have to emissions it.
Look into that. If you can get collector tags that you just have to renew and dont have to emissions, then I would get an emissions sticker with the exhaust you have now and then once it passes, go redo the whole shootin' match to what you want with out the cats.