Crist is correct. Jim makes these beautiful mounts. He used to make them in batches when he received enough orders. I bought two from him a few years ago, and I am still using one in my ECL P-40.
Maybe if enough guys want one he may tool up for another run? They are well worth the $. He made them to bolt into the mount holes of an OS .40 with the E part setup for the standard E motor bolt pattern for our ECL size motors, (ex. AXI 2826-10).
He makes them to very close tolerances. If you get one, you may want to open up the curved part to give you a little more tolerance around your motor. If you mount it "FORWARD" you won't have a problem, but if you mount it "RERWARD" you will have to open the clearance because our motors move up and down more than 1/16" each way when mounted at the rear. If I build anymore CL planes, the motor will be mounted in the front to solve this issue. It is easier on the motor bearings too.
His beautiful aluminum mount is also perfect for nonprofile installations. It will allow you to use the standard MMs. BTW, Jim builds beautiful ECL planes too. :-)