Need help gearing brushless revo

[R00ST]

I am going to hopefully get my 9920 and 7xl from mike (just waiting for the motor to come in stock) and will be running 75% of the time on 14 cell ib3800's and 25% of the time with some older 6 cell gp3300's.

I am at a loss as to how to gear this thing. I am not sure what the ratio of the revo diffs is to the emaxx diffs, so I have no idea where to even start. Another issue is I will be running tires from all ends of the spectrum. I have the 1/8 wheel adaptors (17mm hex), standard maxx sized tires, then also some alrger street tires (40 sized trinity's) and 40 series mashers.

I am a bit low on funds right now, so I think I will have to make the stock slipper/spur setup work. I obviously can then use anything from 66-72t on the spur, but what about pinion sizes? I cant afford to buy all the 5mm sizes mike offers, so if someone (how about you revo-emaxx tranny converters) can give me an idea that would be helfpul.

Hope everyone is having a good thanksgiving weekend!