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In my opinion, the Stage IV is much like the 452 (flat roof) and the Stage V is more like the 906 (arched roof).

That nails it pretty good. I have s set laying around some where and that is what I thought. The stock stage IVs ports seem like mildly ported "smogger" heads without the "Hubber hump" on the port floor. The intake ports are a little taller than stock, but, not by much, and it has a "flat" port floor and low port roof much like a stock smogger. And the pushrods pinch is a little wider than the stock heads. Crane at one time made a slight offset rocker for the stage IVs. The stage IVs have maybe a little more meat for porting so a "Max effort" type port job and big valves may yield a little more flow than a smogger head ported to the same degree. The exhausts look like stock ports, just a bit bigger.
The combustion chamber looks about stock to me. Oh well, this is what I recall