Engine overheating

There is a chance that your radiator is badly clogged or has been repaired enough times that it just doesn't have much capacity. However, that looks like a 26" unit you have there. No reason you should be getting so hot at idle with a 318. If you have no thermostat, open up the filler and look inside there and make sure you see the fluid moving pretty good. If not, you have a water pump problem and can concentrate on that first.