where to measure 273 ring gap in cylinder bore

I'm in the process of rebuilding my 273 HP. I'm confused on where to measure ring gap in the cylinder bore. The factory service manual says to measure 2 inches above the bottom of the cylinder, but I've read other articles that says to measure 1- 1 1/2 inch below the top. When I measure according to FSM the gap is within specs, but when I measure 1 1/2 below top, the gap is at .020 to .021 on compression ring and the oil rails are over .055. Any clarification would be greatly appreciated.