I bought the same model as Jay has but, when got mine, it was to port a set of C6 289 heads so, it needed a little smaller radius. I rounded mine on my disk sander, being careful to stay away from that middle bar but, a smooth radius, up to it.
I later sonic tested my two FE blocks, using the china wall to certify the readings and had no problems with it's repeat ability, going back and forth between the china wall with each cylinder.