Dennis--
I never used the intregal head. Conventional wisdom ,as indicated here, is that the head is prone to cracking. I did have a 71 C-10 with the 250 earlier head and seperate manifold. I had problems with manifold warpage even with that rig. Twice, I had to replace the exhaust manifold due to cracking or severe warping of the manifold.
Finding those manifolds aint easy either--many are warped or cracked and most of the junkyard inline sixes in my part of the country are being wholesaled to Mexico. Gud luk--I wud opt for the seperate manifold.
