Hello' I know this almost 2 months old. But I converted a 3.0 TNX about 2 years ago. I used a align helicopter motor mount. It will definitely fit the feigao size motors. I think they are 36mm. I ended up using a Hacker 3000kv motor which is larger. I just had to shim the mount. I used that because it was a spare. I used 2 7.4 cheapy 8000mah lipos. Only rated at I think 12c. I was stripping spur gears. So I went with the 5.2 35T spur gear. I modified the trans to a single speed. The hardest part was drilling the holes on the motor mount in correct location so it would line up. In this build I got LUCKY took me about 5 minutes, It was LUCK ok maybe some skill too. I had to remove some of the right side of the Trans case to be able to adjust the motor mount. Its kind of a pain but does work. Just need a long ball end Allen wrench. I still have it and love it. it was fast it was pulling wheelies on the original spur set up. I love it. Will be using it again hopefully soon. Its just that I'm in the middle of a HPI baja brushless conversion and a 1/6 Kershaw designs Revo. I would post pics but always have a Hard time doing so on any of the RC forums I belong too. Hope this helps. I wish there was a current Tamiya TNX forum Active as well. I also Have a 5.2 Nitro TNX. Good Luck!!!!