You still have not answered my question. What year is the block? If it is a late model motor home block, it will have the extra cooling holes along the bottom row of head bolts. If you don’t have the matching holes in the 452 heads, it will get hot just like you describe. I’ve had it happen twice on two MH blocks. Water will not circulate properly. I bought all my buddies Mopar stuff the other day because he’s done restoring cars. He gave me his MH block that cause him all the Problems years ago. I have it at the shop. I’ll get a picture and post it for you.