Cooked mmm, well done of course

[lutach]

What is the space between the frames?

You can always ditch the tall tires and go with what most truggies use. You can try and see how it will run with the transmision in there like aqwut and jzemaxx has in his set up. If you do stick with the set up you have, your best option is a long motor with a low Kv.

Now here is what can work with your set up:

Neu 1527/1.5Y (825Kv)
6S lipos
14T pinion
46T spur

That should give you a speed of around 42MPH without tire ballooning.

If you go with a 5.6" truggy tire, then you'll have more options to play with the pinion with the following set up:

Neu 1527/2.5D (925Kv)
6S lipos
14T (36MPH), 15T (38MPH), 16T (41MPH) and 17T (44MPH)
46T spur

I have my tryggies geared for 34-36MPH and they usually go much faster when the tires start to balloon.