Don't feel bad, same for me also the 455's got smogier and weaker after 1974 , you would have to put a good set of ported 6X heads on it or 96/7K3's. Did you see the nice 1973 Grandprix SJ 455 that was for sale in Toronto ?
It was a while ago, now the Kijiji ad is no longer available but I got the fellow's phone #. I sent you a PM. This car is beautiful and well optioned, good luck.
, but I'm looking now.