rpm at speed

i was told a stock motor is about 3 thousand rpm's. i had a tach in my car, but i can't remember at 45 mph.
 
according to graph in Henry's Fabulous Model A, it looks like ~1900 rpm. At 35 mph, looks like exactly 1500 rpm; I would use that slope for other calculations. This is for a 28-29 with 3.77/1 gear ratio, & 4.50x21 tires.

Steve
 
Hopefully Steve's answer is exactly what you needed but if not, several years ago I made up an Excel spreadsheet that showed this in more detail including gear drop-off, etc. This allowed me to swap out different ratios and tire sizes to see how they affect engine speed.

.
 
I calculate 2200 gives 48 mph with 19 in wheels, so 45 would be 2062.5 RPM with standard 3.77 to 1 gears. with 21 in. wheels at 45 should be 1866 RPM.
Each 45.83 rpm = 1 mph with 19" wheels or 41.5 rpm = 1 mph with 21 " wheels.
 
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