My 451 sixpack with mild hyd roller cam and edelbrock heads should make around 500hp so I decided to stay with a stock look and go with exhaust manifolds. The flanges are around 2 3/8 diameter and I will be going with 2 1/2" exhaust all the way back so I was thinking about getting the grinder out and opening up the flanges to the 2 1/2"size. Looks like there is enough material there to not worry about cracking. The exhaust flanges are not that even and I will smooth them out as well and generally just clean things up a bit....... Anybody else do something like this? TBF