I'm using my own motor mount that I made from 7075 aluminum. I also have one of Mike's mounts and it's pretty nice. You can't go wrong with Mike's mount and it makes things a lot easier.

As for the motor, I really prefer the 9XL just because of the heat. The 9XL will get hot too, but not nearly as quickly as the 8XL. Of course, the ambient temperature in your part of the world will make a difference too. If it is cooler where you are, the 8XL might do nicely. It's around 100*F where I am, so the 9XL is what I would run.

If you have the financial resources, I'd go with a Neu 1515/2.5d. On 4S lipo geared at 16/48, is would be formidable on the track. On 5S, it's a beast. On 5S, I clocked my 8ight T at 50 mph with Proline badlands tires geared 18/48.