Hey Capt,
I'm using a Mamba Max with a 7xl motor and a pair of team orion 4800 lipos. I'm no expert but I think either set up you describe will work. As for top speed I think you 'll easily get that 30-35 mph your looking for, you may even get a little more. My project is still in the works so I can't give any stats on what I'm experiencing. I'm waiting on some jammin big bore shocks to finish my truck but I still have a lot of other things to finish.
Does anyone know what spur and pinion combo would work best?
I have a 13 and 15 tooth pinion and a stock count( which I'm not exactly sure what it is, 52 or 54) spur. Also a savage x 2 speed. Any info would be appreciated.
*Capt post some pics if you have them I would like to see your project.*

I not sure on the height of you tire. I run you setup on a speed calculator and
it come up with right at 30 mph with 15 52 gearing. 6 in height tire