I've got a 1965 Nova wagon with a 230 inliner that I race on the occasional Saturday or Sunday in stock class. I run a 4.11 posi rearend and 24 inch tires. The engine has been rebuilt and still has stock valve springs, stock cam lift, Rochester monojet, Langdon headers, etc. I've had it on the chassis dyno which told me that maximum rear-wheel horsepower was 103 and the car reached this point at 4250 rpm. Horsepower stayed above 100 until 4500 rpm and then dropped after that. I usually shift the Powerglide at 4700-4800 rpm but have also shifted at 5000 rpm. I've taken it as high as 5500 without too much trouble. You're correct that a stock 230 will will turn 5000 rpm, but there's not much horsepower up there.
