97 (actually F150 was new for 96. but expanded in 97) is what they were referring to in the text. The old iron lives on as chase units.
You will find 2 major types of truck vehicles in SCORE (baja, etc...)
The Trophy trucks - which are the ones that get the coverage and will the races outright.
and the stockers, which as they say are mostly stock save some changes.
Trophy trucks are like off road F1 cars - massive suspensions that are measured in FEET of travel and can take big terrain at high speed (mad max style) (Very fun to be in by the way but plan on dust getting into places yoy never thought possible). These are the first out at the start of a race, they get the majority of coverage and the big teams use helecopters to guide them. There is a driver and navigator (like rally) but because of the vast terrain and dust the copters steer thier teams through the desert. These ALSO get 3-4 'support' teams - service teams with similar vehicles or older racers than chase the truck and can fix anything in the field should it break down. Honestly its fun but not as challeging as pro rally is for me.
Stockers are restricted from most of this type of support but the companies use it for durability feedback. The factory support guy used to sit next to me years ago so I got allot of the dirt and connection from him.