Make sure the orange and black wires attached to the spade terminals on the coil are on properly and the wire is still connected to the spade inside the insulating boot. Seen them get bumped and broken while working in the vicinity.
The extended ears for the caliper mount on the spindle and the lack of countersink on the hub for the rotor bolts tells me you for sure have the early stuff.
Anyway, for the OP... This is from Bel-Rays website to help clarify weights of motor oil vs gear oil . "A 10W-40 motor oil’s viscosity is actually similar to the viscosity of 80W gear oil, and the viscosity of SAE 10W-30 is similar to 75W gear oil."
You should already have the "L" ones, they hold the radiator too. The holes are threaded from the factory. But who knows what happens in 25+ years to one.