Manufacturers Championships
A championship for manufacturers was awarded to each of the four classes. For the prototype classes, only the manufacturer of the engine was used rather than the manufacturer of the chassis.
Points were awarded to the top 10 on the scale of 20-15-12-10-8-6-4-3-2-1, with exception for the 12 Hours of Sebring which added five points to each position on the scale, and the 24 Hours of Daytona, which added eight points.
Only the highest ranking entry from a manufacturer was awarded points at each event. Any other finishes by that manufacturere were merely skipped.
Read more about this topic: 1990 IMSA GT Championship Season