Yeah, while racing, you'd need a transponder. Most tracks have them to loan out. But you find yourself unscrewing and unplugging it between races. Unless you get a wireless one. But then if you forget to charge it, it's dead anyway. So easiest is to buy your own. They never drop in price though. So you're looking at $80-$100. Sometimes I see them for $65 used.

And yes, for the grid mount, you want inner support for the larger pinions. 17T-22T.