In 24 years, has it run hot before? If not, what is different now?

The mastcated fillers are rubbber type peices that seal the spaces on each side of the radiator. The x-fillers seal the spaces at the top of the radiator, between the bumper supprt and the radiator support. These help channel the air through the radiator, and have been found to make a significant difference.

Switching to a 4 core from a 3 core rad would, in effect, increase the cooling capacity by 30%...so, yes, it would help.

Can you post photos of your fan and shroud?

What is your ignition timng?