[suicideneil]

Quark = no, too prone to overheating and requires extensive modification to run cool.
MGMs = safe bet, reliable, and plenty of high amperage models to choose from.
MMs = maybe, but they really cant take a massive amp draw for long periods.

The V-twin idea is simplest since you already have the escs, but you have to concider that the motors only have very short magnets inside that long can, so they should ideally be replaced with a similar Kv feigao motor, the 7L is 3500 isnt it?

As for the stock truck, once its beefed up to 3.3specs then you can have a bit of fun with it- I assume this race series is an ongoing thing and not just a one-off event. It seems like the VXL escs have the best continuous amp rating of most escs currently available for cars, and they are well priced for their specs. You could experiment with different motors until you find something that pushes the esc and batts to their limits... a couple neu 1509 1ys (3600kv) would be interesting on 3s, and they could be geared higher than the feigaos without overheating as much- then you will find the true limits of the VXL escs.