I have an 81 GMC Truck with 250 Integral Head. I have heard that they are prone to cracking... I cannot verify that rumor. I think people dont like them because they are ugly. They look like they have a Martian Space Helmet.
In addition to the Intake being cast with the head, the intake bolts to the exhaust.
I got an extra Integral Head 250 for $100 this week. I will take some pictures and post them... so then we will both have a clue about these motors.