http://www.superstreetonline.com/how-to/engine/0506-ht-rod-stroke-ratio/Short rods will drive piston speed up too high and dwell time is reduced, the pressure from the combustion has less time to push the piston down - you can't speed up the combustion, it has a duration. If your piston starts moving away from the combustion too early, the combustion pressure never gets to work very hard to push the piston down. With longer rod, you get longer dwell and slower movement after ignition, so the combustion pressure build up has more time to push the piston down (make power).
In an engine that does not need to rev high or that is not desired to rev high, short rods are fine because of how they improve the bottom end performance. Winding short rod engines to higher rpms will cause the engine to "run out of breath" and you get excessive stress loads on the rods, and may end up with failed rod bolts. Wrist pins may wear out the holes in the piston because of the violent change of direction every time it passes TDC. The piston has mass that needs to change direction. Longer rod makes this change of direction more gentle.
A 292 makes enough torque without asking, so much so that you can sacrifice a little of it to allow the engine to breathe better at higher rpms. At this point of a typical build you would have done lots of other mods to justify using higher rpms, and therefore longer rods.
My thoughts only.
Jan
