Temp slowly climbs up?

Ok just got my duster finished,new engine alum headed 410 stroker,reusing the stock 318 with air radiator.Ok the problem, i get it out and the temp stays around a 1/4 the way on the guage get it out and get it upto around 60 to 70ish the tmp slowly climbs up but when i nail it the temp comes back down only when at cruising speed does it climb on me,has new 160 stat new MP visc fan new alum waterpump,i didn't however have the rad boiled and rotted out it seems to be flowing fine.Do you guys think just takin it to the rad shop and having it boiled and rotted out will fix this?