Quick update: Installed racing radiator with a 14" electric fan pulling through radiator toward engine. Running at fast idle for about an hour, about 80 degrees outside, no thermostat, distilled water only. 151 degrees at top of radiator, 135 degrees at the bottom. With fan off, temp quickly climbs past 180 at bottom, but falls back to 135 just as fast when fan is back on. (Gonna have fan running all the time anyway - just playing around...) Fan seems to move a ton of air, and I still have room for a small pusher fan if needed. Temp readings were taken with a Fluke DVOM with a temperature probe inserted into the radiator core.
Of course I need to get all the covers back on and dig some dirt before considering this a success, but so far it's promising. Nothing has been cut or carved on so I can easily go back to the OEM stuff if I need to.