RE: McCoy engines
I had a George Aldrich version of the McCoy 40 Blue Head Stunt at one time. I liked my Johnson Stunt Supreme and ST G21-46 better. I just sold all those last year. I also had a Fox 40 Stunt and a Merco Black Streak. The Merco was pretty but that was about it.
The 2-4 break is pretty much a thing of the past for modern day stunt but the old McCoy Red Head Stunts, OS Max S 35's and Fox 35's sure did a good job of it.