I sent this as an e-mail to someone and they mentioned I should post it here, it was a good idea.
So, ever wonder about all that stuff...here is what I have found out.
Tracker traditionally has had 5 hanger widths, as follows (this is from memory)
half track = 65mm
mid track = 85mm
full track - 106mm
extrack = 130mm (there abouts)
sixtrack = 160mm (?)
halftracks are too narrow for modern courses (well msot), sixtracks are good downhill trucks and people like them on pool decks. mids and fulls are common and extracks are a little less common. Thehalftracks have the most extreme geometry (highest rool center) mid/extracks share the same geometry while the fulls/sixtracks share another geometry (low profile, low roll center). The difference is slight, the pivot is a little higher (like 1/8", if that) on the half (bit more here)/mid/extrack making a turney truck. The fulls/sixs are more stable. The new RT-S is about 1/4" higher than the fulls, same pivot design. The RT-X is a brand new pivot design for tracker (for slalom, shares alot with some of the street trucks).
Where to find extracks? Well e-bay, buy sell trade on ncdsa. oldschoolskates.com , they ain't cheap. If you find them you will be loving life in GS and cruising. The new RT-S 129mm coming out will be as good as extracks, so if you don't feel like searching wait until thanksgiving for tracker to let the bigger RT-Ss out. pictures of extracks (with b-2 baseplates are here).
http://www.ncdsa.com/usr/ur13/leemo_1.htm
Aggros. Well. The "aggro quicktrack" was a hardcore, burly vert truck tracker made in the mid 80s. floating axle, hanger around 160mm (?), the aggro baseplate and the stimulator bushings that everyone loves now...all were from the aggro truck.
What rocks about trackers is that you have alot of baseplate options with gnarly pivots. You have the classic baseplate, the nylon baseplate, the aggro baseplate and the B-2 baseplate...all have slightly difference kingpin angles/height resulting in different turn feel. Out of that list the Aggro is the most extreme angle, the nylon is the next and the b-2 and classic baseplates are about the same. For pictures go here;
http://www.ncdsa.com/usr/ur13/tracker_bp3_1.htm
Tracker has had "gnarly pivots" and "original pivots". The org pivots date from the 70s and many claim have a better feel. But when vert/pool/street skating hit int he 80s the original pivots always broke so they beefed it up to the gnarly pivot. I prefer the ganrly pivot turn feel. Here is a picture of the difference;
http://www.ncdsa.com/usr/ur13/tracker_s_w_1.htm
rad pads...WELL...ebay is your only bet for these. They are rubber wedges dateing fromt he 70s, chris yandall and wayne brown signature ones. They came in a few different sizes. System 1 (the one I like) was a 8* front and a 14* back, soft for dampening on stiff decks (like the stiff turners I ride them on), system 2 was two 8* wedges, softer rubber for flexy decks like fibreflexes. System 3 was flat urethane and system 4 was about 7* for freestyle. I paid over $60 each set on e-bay for these. I've seen them go as cheap as $20 and as much as $100. Here are pictures;
http://www.ncdsa.com/usr/ur13/radpad.htm