yes, that the abutment, the caliper assembly is a 2 piece assembly. If you look at my brakes on my site, you can see it is the shiny black piece. Not sure about the fins doing much, but it gives the caliper more surface area which allows the heat to disperse more. You can come across C5 calipers so easily and cheaply, I dont see the reason to go with the F body ones, unless you they were free. If you shop wisely you can get C5 rotors at napa for I think like $30 each, then all you need is the calipers; ebay prob like $100 for the pair used, then all you need is good pads; $150. This will get you in the door, and you won't have much of an investment. Then down the road you can spend some real coin on a real set of brakes, but you will probably want some better wheels/tires then also, and you can get a bigger rotor etc at the same time. Whether on a bike or car, I know that on my first time on the track, I barely even used the brake!!
Just learning what turn is coming next, and how to get setup for it, takes enough of your attention away. But RA looks pretty easy to remember, and you will be needing some good stopping power on that straight away!! Just get some good pads, that will be the key factor, you might go to a vette site and go to the trackday section and see what people are using;
http://forums.corvetteforum.com/forumdisplay.php?f=23