rear gearing with a four speed A833.

Alpha
Your thinking is a lot like mine.
Id like to respond to the questions about long engine life.
Todays modern engines last longer for mostly 2 reasons; 1)better oils, and 2) MPFI. Fuel injection is better able to control the fuel charge and therefore a lot less of it sneaks past the rings and into the pan.When the oil stays on the cylinder walls, the rings dont chew them up.And with the oil in the pan being now mostly oil, the bearings last a lot longer as well.Prior to about 1970/71, our Mopes did not have the hardened valve seats. When these engines were forced to run on unleaded fuel, the soft seats had a much reduced life. So typically, those older engines would be well past there prime by 100,000 miles, and looking for retirement by around 140,000 or so.Timing chains were often done a lot earlier.Now modern engines, with electronic controls are also better able to control ignition as well.
-All this leads to the right amount of fuel being in the chambers more of the time, and all of it being burned more of the time.
-If you would take one of those early engines, install hardened seats, and MPFI, and load it similarly to a modern cars loading; Id be willing to bet that its life would on par with modern technology engines.
-Conversely, if you were to take a modern engine, slap a carb on it,take away its computer timing controls, and load it up like the old days; I am pretty sure it would die as early as they used to.
-I think this longer lasting business was a side benefit we got ,due to the struggle with pollution control.Pollution control demanded better fuel control and better fuel economy. This led to longer life, lighter cars,and lower gearing
At least thats how I see it.
-And youre right on target;To be competitive in every arena; performance, economy, long life,etc., we need more gears. VVT would also help