over heating 440

Over heating 440 in my just purchased 69 dart. has B Cool rad. .600 isky roller
w/ .300/.300 lift, chrome headers etc. Car runs cool at idle indefintely but I was told that after 30 min. of hwy. driving it will get to 220 and wants to vaporize the fuel when you return to normal stop and go traffic. Any thoughts, opinions or facts would be appreciated.
Thanks
Pushrod