RE: Cox .074
I got an .074 at a swap meet with a Jr. Skylark or Skyhawk or something like that. I could not even get it going and was kind of mad with the motor. I took it out to replace it with a Norvel .06 after a few years, and tried the motor on the test stand and it runs fairly good without the muffler at least. Maybe I'll put it back. It is a reed valve motor though so it is no ball of fire. I got 15,400 rpm on a 6-3 1/2" prop without the muffler. I would rate it about like a worn Tee Dee .049 with a better throttle. I wouldn't reccomend buying one, but you have it already like me, and they are ok for sporty stuff. An AP .09 ASP .12 or almost anything would be better, but run what you brung. I think any .049 sized plane would be fine with that motor, but a .10 to .15 size plane would be anemic. There are lots of plans and kits for .049 stuff likely here on rc groups. Even some ARF electric planes should be good to convert.