This swap is more benficial on a BBC. The #2 cylinder and the #7 cylinders are on the long runners and on opposite ends. This is a particular issue with leaning out #2 because it pulls air/fuel after #5 and #7. So the strong sequential pull to the back end is followed by #2, and #2 will run lean.
The improvement by making the firing order change on a SBC is not as great because the intake valves on the end cylinders are on the inboard. But there is some gain since the air flow change goes from the back of the engine to the middle, instead of to the front as in the "stock" firing arrangement.