The powertrain chart in the GM Heritage Center archive shows the 2.73 axle as base (special order not required).
http://www.gmheritagecenter.com/gm-h...let-Blazer.pdf
see page 2 and page 6.
Engine RPM at a particular vehicle speed is calculated as follows:
N/V = [Tire Rev (rev/mi) x Axle Ratio x Trans Ratio] / 60 x V (mph)
N = engine rpm
V = vehicle speed
Tire revs is in rev/mi
Trans ratio would be "1" for high gear
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