Sounds like you are well on your way. I'd be very wary about trying to save a few bucks and going with a no-name lipo. These things are finicky enough without having to worry about quality. For bashing Maxamps are pretty hard to beat. As for trays, people here are quite resourceful and you can get a lot of ideas by looking at the different built threads. I have a few different conversions and every one of them has a different battery tray. One fabricated out of aluminum angle, another hacked out of an e-maxx chassis, and another using Kyosho Twin force trays (which are available through Mike).
My Revo is set up for racing and I use first gear and mechanical brakes. 3S is plenty for my track and I can get a 15 minute main out of a 3S 6000 mah pack.