I hate to see you pull the heads if you don't actually need to. On the other hand, I was working on a 360 a couple years ago that had a horrible exhaust leak, and in the process of getting manifolds off I managed to break three of the bolts off in the head on one side. Since it was the manifold flanges on the head that were badly warped (worst I've ever seen) there was no way to make it seal without getting those surfaces flat so I had to take the heads off. That made it much easier to get the broken bolts and get them out, and I discovered when I got the heads off that the head gaskets were rusted almost all the way through and one of them had less than 1/8" of material left between the cylinder and a water jacket, so those gaskets didn't have much life left in them anyway.