Well for starters will give you all the info I can about my 94 Z28, I just rebuilt the motor (wait a pain that was) and the car runs great now, but after it was rebuilt I noticed my fans where not kicking on and took care of that using a pcm bypass switch to turn the dual fans on. My car has a brand new water pump, 160 degree thermostat, running 50/50 coolant, new coolant temp sensor. Turns out all is still not well my car still gets crazy close to overheating but only when I am driving it, but I have no issue when I just start the car, barely any air circulation and let it warm up and rev it up for the hell of it while in park the motor struggles to get hotter than 175 degrees. I have tested and know the thermostat, cooling fans and water pump are working properly. Open to any suggestions or theories as to why this is happening?

Now here are a some ideas & theories me and some of my friends have tossed around.
Might need a stand alone transmission cooler, since my trans cooler is built into the radiator.
Might need a hi-volume water pump
Might need a better radiator
Might need fans that push a higher cfm than the stock fans

 

Might be your front air dam is missing? That helps to move air to the radiator while open road driving.

 

Turns out after taking a quick look under the front of the car It's missing.

 

one guy on here made one from stainless, i think in shop class, looked pretty good.

 

You may also want to return to a stock temp thermostat. These engines are meant to run hotter than the old first gen SBC. You don't gain anything with a lower temp thermostat in a stock build.