You made a nice conversion, But if i may be so free to criticize; (please don't take me wrong)
I would only use it with lipo's, because with heavy nimh cells, the balance will be gone. With the 4S2P packs you are using it already is out of balance.
That batterietray doesn't support the batteries to fall out in front or in the rear, with bashing you really want your cells to be put on tighter than tight.
The speedo is placed on a forbidden spot, it is a treasure, you want it well hidden for impacts. if you crash your conversion like this, it will be bye bye speedo if it took a wrong hit.
Have you seen
this sexy conversion?
I have seen a movie of the hvmaxx on 4S lipo, and i sure was impressed! in fact; i am thinking about buying one for a lightweight bashmaxx. It is one nice setup. About the gearing, i think you are smart enough to look up the used gears, and calculate the gearing ratio. Without the pinion/spur the gearing ratio of a stock e-maxx is 5 to 1. and the advice Novak gives on their site can be used on your revo too.
Sorry for being so hard on you, it isn't my intention, but i think when you sell something it needs to be perfect, don't you agree?
Daniel did a perfect conversion on his revo, it uses the stock maxx transmission. (which gives you a nice 2 speed and a motor brake)
You might consider using the mechanical brake, it will be even quicker with the 2 speed and the mechanical brake will be easier on your controller as well. (so the controller gets less hot)
Again, sorry for being so straight forward..