I had the same problem. Repaired using Dick's recommendations. I used a small ignition wrench at the raised ridge on the tubes to hold them in place from inside the exhaust runner while I swaged from the top.
I did use just a touch of hi-temp Permatex around the edges as I never could get the tubes as tight as I was aiming for. Just didn't want any exhaust escaping around the edges of the tubes..
