I have got a really narrow gauge but I am thinking the fans are running right at 185. I can't hook up the sending unit from the fans and the gauge at the same time because the adapter for the temp gauge in the intake manifold is siezed in there. So I have to use the narrow guage instead of hooking up the stock guage.
IMO I don't think its detrimental to the flow at highway speeds. My car would actually get hotter when using the stock fan/clutch setup. Until I installed these fans and radiator I would never see anything below 200. I averaged about 210 and warmer in the freeway.
I don't know how much you know about these vettes (don't mean that in a bad way) but you'll find out these things run hot.
I will say this...
I have spent about $9,000 restoring this car and Have done about 90% of the work myself.
I had problems with the car running VERY warm 200+. thins is what I did that now keeps it at < 180 even on the highway @ 65mph and 100' day.
REPLAECED the radiator with a 3 core (1'' tubes), installed a 165' thermostat, new water pump(nothing fancy), cleaned up vacume leaks, tuned carburator, and set timming correctly. I even went as far as to install a 16'' fan and thermostat that screws into that block (can't remember the setting on it though). Installed New aluminum heads, cam, headers, MSD 6A.....
The car WON'T overhead anymore! Even sitting in traffic!! There is one problem though... the driver gets overheated (LOL) I guess my next project is going to be the ventalation system!!