Resonator delete and exhaust cutout

I have a 1996 Buick Riviera s/c. My buddy has a exhaust cutout, and we were going to put it on the Rivi. My first question is: Does anyone have the exhaust diameter of the resonator section? So that if I was to remove the resonator, what size pipe should I buy for proper fit? Also, are there easier methods of sealing the pipes without having to weld? (I can weld; I just would prefer to steer away from dropping the exhaust if at all possible) And finally, as long as I locate a y-pipe cutout after the cat. converter, will there be any negatives other than noise?
Thank You.

P.S.
This is my first post in the AF.