I am not sure the engine mount that I got is something you can buy at the LHS, Mr. Wolfgang himself send me these goodies.......
However, you can definitely get the .15/.21 engine conversion from Wolfpack...........they are like $60 with engine mounts and flywheel......
Since I sold my Centax, I cannot tell you the correct answer, but I can guess the Serpent CENTAX will work on this configeration but ONLY with the adjustable engine mounts, because no matter what you do, SG crank engine is good 10mm to far from the 2-speed gear box on HPI cars ONLY IF you are planning to use the original engine mounting points.