Well since there isn't a significant air mass moving over the engine/radiator at a stand-still, most engines heat up more than while moving. This along with the fact that these mitsu engines are known to run hot may put it in a tight spot.

Exactly how hot is it running? Just don't let it hit the red, think about a coolant flush maybe at least. Replacing an old radiator is also a good idea, but $$

87' Raider: off road package, rebuilt engine with (new) stock tires and alloy wheels but otherwise original.