I've run a 2wd SC10 for a long time now, the stock tyres work just fime on astro, they used to be the hot ticket, before the advent of the Kourse King, whic is what most people have been using on the Astro tracks during the UK SC Nats.
Can't help you with much else TBH!
In general people have been running 550 can motors in the 4wd's, but the majority of them are chunky alloy chassis trucks, from memory I have seen 2 4wd SC10's during the series, but I can't remember what electrics they where running...I think one of them is on Oople so I'm sure he will chip in here.
FYI I use a SP GT2 with a V3.0 7.5 in my 2wd, and it gets pretty hot
