I have never had to even dimple a Hooker 6114 on a Mustang, over 3 sets in different cars, all 4 speeds, although I have never used any of the race headers. FPAs, the only thing I had to do on a 428 Montego is put a bar inside the collector and pull it slightly to center, on a 460 big body Mustang they slid in, although a 67 F100 we had to take about 1/4 out of the upper edge of the frame rail.
What kind of car is it? I think I missed it