The 2-speed rear end gives you two speed options- - - -slow and slower. Put a tachometer on it and keep the top RPM around 3,000-3500 for the best horsepower. The 292 engines from the mid-1970's are HP-rated at 3600 RPM, so winding the engine tighter than that is futile. Even if it runs faster, you're above the horsepower peak. Keeping the RPM between 2,000 and 3,500 will give you the best performance, and the 2-speed should allow you to do that under most normal operating conditions.
Jerry
