How can I modify my y-pipe ends to install the 3 bolt connecting flanges for sbc headers?

Okay i bought a set of headers for my iroc-Z and they fit directly in place of my manifolds. The only problem i have ( knew it was gonna happen) is that the flange to bring up the y-pipe is 2 bolt and the pipe is lipped so it cant slide off and helps connect to the manifolds. is there a tool i can use to bend the lip back straight so i can slide the old 2 bolt flange off and put the new 3 bolt one on to accept connection of my new headers. sorry if i sound dumb or confusing