i did some work on a 36 years ago 350 with a 671 blower then a hi cr 383 with AC it never ran hot that i knew of i think it had all tin inners in it. after the 383 the guy ran the car threw his cement block shop and i fixed the car . it had a walker rad in it . with a big puller fan . how is the tune up on this engine ? vacuum av will help engine run abit cooler at ide water speed . it may like the water to move faster at off idle