[68 Firebird]

I admit that cooling my car over the years has been fun.
what i can say is all the parts must work together.
Mine barely hits 170 thermostat unless on highway when temps are over 85-90.
Using the following
Cold Case Aluminim Radiator(2 rows 1.25" tubes)

AC style pulleys to overdrive fan and Cooloant(major improvement at idle!!!)

When overdrive pulleys were installed the 5 blade factory fan became noisy(more RPM)
it now looks great as garage art along with original Crank and WP pulley)
Also have 11 bolt pump and timing cover installed with tweak to divider plate.

installed 7 blade AC fan from 76 TA found hayden STD duty fan clutch worked fine(tried HD and SD)

HEI curved conservative 10 initial 32 total(comes in at 3500, Heavy HEI springs)) 14 from VA on ported.
Qjet i rebuilt with parts from Cliff, no issues.

NOS Delco thermostat 170 that actually cracks open at 165, fully open at 180.Checked on stove before install.(superstat worked well as well)no holes drilled in stat.

no issue with trans cooler use in radiator as well.

mine runs just under 170 when cruising around and NO increase while stopped in gear.
much of this knowledge came from research on this forum.

Good Luck
Gerry