[bdebde]

1) I would recommend a Neu 1515 2.5D for 6s. If going Lehner, a 1950/7 should be good. Stay around 40,000 rpm for whatever motor you choose.

2) The high amp version is the only way to go, the small plugs really suck on the standard models.

3) Don't get the cooling system, you will only suck dirt into the motor. The Lehners run plenty cool if set up properly (gearing,voltage).

4) I like the Neu's because made in USA (not concern for you in Aus), easier service. They are all excellent motors ( I have 1 or more of each), pick whichever you can get easily there.

As far as running the Big Maxximum on 6s, they can handle 75,000 rpm max, but I would not do it. I have run a Big Maxx on 6s in a 13 pound Muggy with a center diff (30K fluid) and it spent so much time on its lid that it was no fun. If you run that set up in a truck with a transmission instead of center diff, it would be even worse. I went to a Neu 1515 2.5 on 6s and am much happier because I can actually drive the truck instead of going to flip it back on it's tires all the time. The Big Maxx would be perfect on 5s, it is just too much on 6s.

Keep the RPM around 40,000 and you will have plenty of power. The Lehners make the most power and have best efficiency around there.