JMP T-33
The by-pass for my JMP T-33 has a diameter of 5.75 inches. I have seen two of these aircraft powered by the AMT Pegasus, which I believe is larger than the KJ-66 derived engines, so any suitable engine should fit. Also, they did not have a problem with heat in the upper fuselage or tail. The JMP by-pass and stainless steel pipe cooled very well.
Roger