It will have reverse, its just done with the electronics and not the gear box. The plastic axles wont hold up to brushless power, especially if you're going 6S, which is what most people do with 1/8 scale rigs. If you go 4S then you can try it and see how it works but Id speculate that they will...
I've never done an E conversion to a TMAXX yet but at minimum you're going to need an 1/8 scale ESC & Motor like the Castle Mamba Monster 2 and Castle 1515 - 2200kV, a motor mount, Battery tray, 6S Lipo, You'll have to do a single speed conversion and a forward only conversion to the transmission...