1978 Nova Overheating

I have a 1978 Nova with a 305 engine. Running temperature is about 215 degrees, but spikes to over 230 and higher when idling for a few minutes. There is no shroud around the fan. Any ideas on what could be causing the overheating? Manual states timing, radiator clogged.... Radiator was in the car when I purchased it. Non running car and had been sitting 20 years. Complete engine overhaul.

i would check the Radiator have it flushed.

The proper fan shroud will make a huge difference.