Fox engines have had a lot of bad publicity, but no one remembers the dog or two that OS has made. (Remember the famous air leaking .61 fp carb needles?)
Have a friend who has flown r/c for over thirty-five years, has had fox for at least that long of a time, he sez he can't find any stronger .74 size engine than the Fox Eagle.
I have an Eagle 74 myself, look on www3.bc.sympatico.ca/Flite Line at the specs for the 74.
To sum up the specs more or less, if the prop will fit on the crankshaft, the 74 will turn it with good authority.
As for why they aren't found in too many hobby shops?
Fox does not have high production capabilities (probably) and I don't think they have the financial backing that OS enjoys.
In closing, the first schenurle port engine that I seen was either a a fox 40 or 46, and due to the backplate's oddly shaped design, they were often called "coffin back engines".
Just my .25 worth,
Gary Smith
