Awww, how sweet
To do it the right way, send the tube you need to fit well to Stainless Works. They can swedge tubing to thousands to fit perfect.
It's what I had to do for a client's megaphone exhaust to make it fit perfect on the termi pipes (replaceing the carbon cans with stainless megs).
Wow my termis are loud, I can't imagine what those sound like. I had megs on my 305 superhawk back in 71. They look great BTW