Thanks everyone. I will try this again tomorrow with better info on timing and temps. I'm living in an apartment in Nashville now so I do the best I can with having no garage and all of my tools in storage. Here's answers to most of the questions posed so far...
Cam...Comp Cam basically a newer version of the stock cam. (hydraulic) Timing..."it's good" I threw a light on it and the marks were visible. I was pissed because I didn't think to get my distributor wrench while picking-up the timing light from storage so I gave-up on that. I'll get the actual numbers on it. Block/Heads...Recently rebuilt motor not more than .040 over. X heads. Fan...Stock fan with clutch. Fan turns all the time. Clutch is not slipping Radiator...Stock re-cored rad. 1WildRT mentioned baffling. Yeah, there is a baffle at the top so you can't see the fins/passages. Shroud...Yes Thermo...Have not removed/tested it yet Lower hose spring...All newer hoses. I don't see any collapsing of the hose. Water Pump...again, everything is new, BUT something that has been troubling me is that there is always corrosion around where the heater hose connects to the top of the pump.
The video is the only thing else I have to offer at this time. Thanks again. Can't do video here, so here's a YT link...
Video set to private. At any rate, when I first got my 64 Valiant, it did very similar. As soon as the thermostat opened and with the cap off, when I revved the engine, it would blast out of the radiator filler neck. If that's what yours does, I would have the radiator checked for flow. Mine was stopped up, giving the coolant coming into the top tank from the engine nowhere to go. Just because something is assumed good, means nothing. Keep that in mind. As soon as you say, "the radiator's good" you're setting yourself up. Keep an open mind.