Well, the blade 400 has only a 10 tooth pinion.

I purchased a 3.17mm 12 tooth pinion (Align) but the inner diameter if the pinion is too large for the blade 400 motor's shaft....

I'm also concerned about the motor mount screws that come with the EXI. The motor mount screws for the Blade 400 are Socket Head Button Screws M3x8mm. I'm not sure if the EXI motor mount screws are the same, I guess It doesn't matter as I could always dremel the motor mount on the EXI...