You don't say how much you shaved the heads, but without the head shave, the compression ratio would have been 8.4:1 and the 268 cam would be a little much for the motor. It may be a little soggy on the bottom end compared to a little shorter cam. On the flip side, you probably didn't set the squish at 0.035" to 0.040", so the bleed-off of the longer cam won't allow the motor to build cylinder pressure to the point where you might worry about detonation either.