[Double Stack]

The engine is a rebuilt 69, 350, four bolt main.

The last time I checked the spark plugs was about 200 to 250 miles ago and they were good.

I haven't replaced the intake, but this is a fresh build. I picked it up with something like 6 miles on the new dash/engine.

I just checked out the water pump like you said, and if i'm looking at the correct hole everything looks good. See pic.

My radiator cap looks new, and I don't have the adapter to check just the cap. I guess I could buy a new one and cross my fingers.

I will say that I've been having this problem since the long drive home when I first bought the truck.

Thanks for all the ideas. I really appreciate it.