RE: Norvel .061 vs Hobby People AP .061
The AP is a cheap knock off of the pre-revlite Norvel. Most of the issues have been addressed here. The major issues are low machining quality (hence the wide varrience in quality and performance) and much lower quality metals, which is why even the "good" ones go to an early grave. Some parts are technically interchangeable, such as piston/cylinder sets as a whole, but now that Norvel parts are available again, why? The carburators are round, not oblong so the carbs and cases will not swap. I have tried swapping some of the parts, but have always ended up with lower performance and wore them out quickly.
It is similar to when Toyota copied the old 50's Chevy in-line 6 cylinder for the LandCruiser. With the inferior metals and machining, they all blew up early in life. The good news was that the bolt pattern let you drop in a small block Chevy when they did blow up, and by then all sorts of stuff like fiberglass tilt front ends were available! (Can I get an "Amen" here CP?)