The Briggs model 140000 motor started with a HP rating of 5 3/4hp, and was upgraded to 6hp when the coil/flywheel polarity was changed. This caused a lot of confusion when ordering parts. Information on this motor was left out of many Briggs manuals.
This ad states the motor was "Tecumseh 6-HP all aluminum motor". You may notice in the 'EQUIPMENT AVAILABLE'... "Optional 8 1/2 HORSEPOWER Gov't Rated 2 CYLINDER MOTOR (Special Order Only)". I wish I had more information on that option.
The shrouds on the Briggs 6hp, 7hp and 8hp motors ARE interchangeable. Many people like to use the 6hp shroud because it is embossed. Also a shroud with the cast spring housing is better because the rope spool is cast metal instead of plastic.