Hello there... got bitten by the R/C bug again?
I know alot of people in 2WD tend to run either a 6.5 or a 7.5 brushless motor and the brave or talented maybe a 5.5
What sort of racing you planning on getting back into? Regional level? Club level?
If you are only wanting to run at a club level I would probably take a trip down to your local club and have a nosey at what the other guys there are running.
There are a lot of brushless combo's on the market at the minute which you can pick up for a fairly descent price
A quick example is this combo from JE Spares, but a quick search around and you can get some really good deals...
http://www.jespares.com/electric-mod...tegory_id=1276
Hope this helps a little lol