Can you access the McGregor mountain trail from the Stehekin Airstrip?
Sure. Just follow the road from the airstrip to the major road going up the valley to High Bridge where the trailhead is located. The airstrip and the mountain aren't really close to each other, despite how it may look from this photo.
i live a couple hundred yard from were you are standing during the summer. i live in one of the cabins between the airstrip and compactor (stehekin mall)