Duster 383 cooling issue

No hood to radiator seal. CFV said the pulleys were 1-1 ratio. I’ll check for cold spots In The am it is 110 out side rite now. but when I start it up temp rises to 180 then goes back down and then up to 180 and back down again before it starts climbing past 180 to 200 at idle. But when I put it under load and drive it climbs to 220+
Pulleys measure 6.5-6.5