87 over heating

[bradley]

need some input here the wifes 87 gt 5.0 302 is over heating you get now warning. i was told to check the thermastat in it well i pulled the hose and there is not one in it. so that knocked that problem. when you are driving down the road the whole car shuts down no warning or anything then let it sit 30 mins to hour your good to go for about 10 miles lol. I am going to replace the water pup and raditor then put in a thermastat. if this does not fix the problem what do i need to check next? the head's think they could be cracked? if so how whould i check that im new to working on cars but really want to learn how to do it on my own.... 8-)