[Patrick]

Since money is a factor I wouldn't worry about spending $150 or so on the stampede trany and hope that it works.
I would look at geting the t-maxx trany to work, but I know nothing about them so I don't know how hard that will be.
To build a 2 speed e-maxx trany from scratch with steel idlers I think would be maybe just over $70 (with stock motor plate) plus what ever slipper setup you get. If you only want one speed add about $12 for the single speed coulper (you can make it single speed without it, but it will be stronger and smoother with it), but you won't need the $13 1st gear idler or 1st output gear (I think about $3-$4).
I think to build the Gorilla Maxx single speed transmission conversion (only uses on half of the standard transmissin) would be about $100 plus slipper.
There isn't really any need to get an alloy transmission case for the e-maxx imo.
You can get some of the stock transmission, motor plate and slipper parts fairly cheap of ebay sometimes though.

Once you decide to go brushless do some more research here (theres a lot that can be learned), most people will tell you there are better, cheaper systems available than the novaks.