I own this old duster now. About the only thing that is left of it is the fuselage and the paper work.
In the 50s and early 60s, there were a number of small crop dusting services that used modified J-3s. At this time one could buy a J-3 for a few to several hundred dollars. These modified J-3s could then be sold for $1000 to $1500. While my Father, Ed Shumaker, worked for Graham Aviation, we has a hangar and small strip on our property; as a sideline, he would convert J-3s to crop dusters. My job as a teenager was to stand inside the hopper and buck rivets. Later my younger bothers took over this job.
After Graham Aviation closed, my Father and Bill Singleton started S and S Air Service. Their first two aircraft were this J-3 and a PA-18A. We named it the "Stump Jumper", and the PA-18A was named the "Spook". This J-3 was already converted when they bought it. I don't recall which engine it had initially, maybe a C-85 or a O-200. When I got to fly it, the engine was a "hybrid" Lycomimg. This was a O-290-D with a carb and oil sump from a O-320. So the engine had two data plates. The O-290 data plate on top of the case like the A-65 and the O-320 data plate on the oil sump. When this engine needed an overhaul in the middle of dusting season, the "Stumper Jumper" borrowed the O-235 from our PA-12. Working aircraft have priority when it came to available engines.
The few times I got to fly it was a great thrill. With no load, it would be ready to leave the ground almost as soon as the throttle was all the way open. Some operaters claimed the semi-open cockpit with the leading edge continuing across the cockpit made for more lift.
Once when Bill Singleton was dusting with the "Stump Jumper", a "June Bug" (colloquial name for a iridescent green beetle about 1/2" long) went over the top of the little windshield and under his helmet hitting him directly in the forehead.