Lol, it's been a frustration for a long, long time. It's not really a matter of parts or options (for the most part) - it's some mysterious process that's not understood by anyone.
But to set the record straight, there are over 4.7 million permutations of a TRX order.
3 level options (Base, Level 1, Level 2)
6 color options
18 individual boolean options (yes/no) such as Rambars, Bead-lock capable wheels, etc.
3 x 6 x 2^18 = 4,718,592.
Not that it matters, because they just draw VINs out of a hat.