"Worst" combination Chevy had in my opinion was the older full sized Impala's and trucks with a drivetrain setup like a 283,or 307,327 V8, a Powerglide 2 speed automatic,and a rear diff with 3:08's or under ratio,which was probably the most common...
The vehicles had sluggish take offs and the transmission still shifted into drive at 20 mph or so,and usually would not downshift unless you floored it,when it "lugged" in drive,the torque converter was what took the brunt of the load--amazingly few ever failed,but I bet they ran hot in hilly country!...some Powerglides in 4 and 6 cylinder cars like Nova's and Vega's were air cooled too--NO cooler!..just fins on the torque converter...
A friend had a '67 Impala "Fastback"with a 283,2 bbl, and the Powerglide trans,and 3:08 gears..got it from his grandmother,nice car too...but a dog as far as any "performance"..it accelerated adequately in normal driving conditions,got decent gas mileage,maybe 15 mpg or so,but as far as being "exciting",the car was not much fun..
That soon changed when my friend bought a wrecked '69 Camaro for parts and took the bellhousing,and 4 speed Muncie transmission from that and installed it in the Impala...took him about a month of salvage yard hunting to locate a complete clutch pedal setup for the Impala--(they swapped him even for the setup out of the Camaro!)...he found a '66 Belair with a 250 six three on the tree that had all the right parts)..
He left the original rear end in it though--the transformation was still quite impressive,the car took off like a rocket compared to before despite the tall gears,it could wind up to about 55 in first gear if you held it floored before it topped out,and could still bark the tires upshifting into second and third from a standing start...if you wound it up and dumped the clutch it would burn the tire (no posi!) for about 200 feet until the car caught up with the tire speed...
I remember him telling me he took Grandma for a ride in it after the conversion ,and she was quite horrified when he booted it to get on the highway..

...