Although it's not overheating, I can't get my 451 A-body to cool down to near the thermostat temperature while moving. 4-speed, 3.91 gears.

I have a 180 degree Milodon high-flow thermostat, Contour fans mounted to a 26" radiator. (Originally a stock Stant thermostat and an old 26" copper-brass rad, now a brand new 3-row aluminum. No change).

Too much cam, but plenty of timing (27 at idle, and vac advance) so it's not ignition retard. AFR tends to run in the 13's but not pig-rich.

The fans are controlled by a nominal 195 temp switch in the upper rad hose, so I expect the temp to rise while sitting still, then drop back down (and it does, from 198 to 192). Since I tried the aluminum rad the gauge comes down faster once the fans kick on, and the swing is the same. I can lock the fans on at idle and get down to low 180's. So far so good.

But while cruising at 14" vacuum (35 mph @ 2000 rpm), or 60 mph @3000 on the highway, the temp will rise until the fans come on, but will not come down below 194 and shut them off until I sit and idle long enough to get the accumulated heat out.

What's left but the water pump? I do have the 0.95:1 fan/crank pulley (water pump slightly slower than crank) for non-a/c cars. Can't remember if there are six or eight fins on the pump - it's a generic rebuilt from the chain store. I would have checked this while the rad/fans were out, much easier access, but was convinced the radiator was just silted up and too many tubes blocked.

So I'm considering a Flowkooler high-flow water pump (rather than change my pulleys and belt, especially since I will be shifting at 6500 or higher).
Any thoughts?