For onroad, I would use the Monster based stock....if the track is big and very wide open, you can use a ROAR based stock...
Our stocks come with 767 brushes, which is what we use at most tracks....those Flines are popular though....
As for springs, your motor will be tuned for your type of racing.....just select it on the site.
As for a turbodyno, just get the 30.....turbodynos are hard to find as it is, no need to be picky, especially when you can just send it in to CE and get it upgraded to to a 45 amp version for $100....which is really only need if you plan to test modifieds....
XXX brushes take 5-10 minutes to break in....I do it at 2 volts....takes a while, but just check every minute after 4......
1/12th scale motors are wound different.....we use different gauge wire to get maximum efficiency, while maintaing a smooth power band....for timing, I would start at 6-12 degrees....adjust until you get slower and/or dump!
Later EddieO