Project 440DD

Question..... I was doing some measuring on the dart yesterday.... the opening for the radiator is only 22.5 inches wide. I'm gonna be running a 26 inch, 4 core radiator to keep the big block cool. My question is, should I try to cut the opening larger by 2 inches on each side?
? I don`t know, but I`ve got a 28x19 crossflow, w/ 2 rows of 1 1/4" tubes. the core it self fits the stock opening on my 68 fastback. I`ve wondered if cutting the opening out to let air hit the tanks woud do very much good>??????????all opinions are welcome.