They are a very good cast pistons and they will take some boost but forged is better for any serious boost.
Could be the Paxtons make more boost because they found a better impeller some where. Maybe some trusting soul sent them a prototype to test and.......
The older McCullochs can be used with the clutch and solenoid set up that in theory makes them progressive or they can be converted to direct drive like the ones used on Avantis and Larks. Brackets are not hard to make and carbs are not too hard to modify or just change the floats and put it in a box.
