Along with the photo, try to post some measurements. That may help identify it.

When it comes to engine choice, it would be a sin to put a 2-stroke glow engine in a cub. If you go glow, a 4-stroke would be the way to go. Something like a 1.20-1.60 should work I'd think. It may be pricey but something like this would really be cool: http://www3.towerhobbies.com/cgi-bin...?&I=LXBY68&P=0

Another option that is pretty budget friendly would be gas. Something in the 20-26cc range should fit in the cowl nice and fly the plane very well.