92-94 models got fixed headlights. The 90-92 engine had beefier rods than the later cars. The crank had heavier counterweights and larger bearings, and attached to the flywheel with six bolts, compared to seven in the 93-94 cars.
Pistons are different in the later model years to match the thinner rods.
90 cars had an external oil cooler. 89-91 cars had a smaller rear axle design that attached to the hub with three bolts. Partway through the 92 model year, the factory switched to a larger axle with a four-bolt hub attachement. These break much less at the drag strip.