If the K&B is the BUSHED BEARING type, you should be OK powerwise. The bushed 61s had about the same power as a ball bearing 40 - 46. Don't forget to rebalance the plane. MOST 61 engines like a 12x6 prop, so make sure you have adequate ground clearance.

How did you manage to "kill" the engine ?

JB Weld usually works well. The key to getting it to work/adhere properly is to make sure the surfaces are CLEAN. I recommend using acetone to clean the part(s) and DO NOT HANDLE THEM on the surface to be glued - the oils on your hands can (usually WILL) cause a poor bond. One other thing - use the regular JB Weld. The 10 minute stuff, at best, has only 1/2 the strength of the regular stuff.