2.66 low gear vs close ratio

Ok, so this is something I have first hand knowledge, since I have run all three, er, all four,er all5 ratios.Yes there are at least 5 ratios in the Mopar 1x23 sbm box; and I've run them all.
Here's the key; the ratio to run needs to match the intended useage and the engine powerband needs to match the chosen ratio.This will give the best results.
Here are the ratios,from memory;
2.66-1.92-1.40-1.00 This set can be had with a 3.09 low
2.47-1.77-1.34-1.00 the close ratio box
And then there are two O/D boxes
3.09-1.67-1.00-.71od This box can be found with a .73od

The shorter/lower the operating range of the engine, the wider the ratios can be.
The higher the rpm of the power band, the narrower or closer the ratios need to be.
If you are racing with a very narrow powerband, the tighter the ratios HAVE to be.Or the powerband needs to be adjusted for the limitations in the ratios.

for a streeter, the wide ratio 2.66 box works just fine. A streeter usually runs a 240* or less cam, and is limited to 60 or 80 mph, and just two or maybe three gears.If a streeter is running a smaller cam than that, and wants to cruise in comfort, then the 3.09Low box can be put to good use, with 3.23 or less rear gears. In this case a 10.xx/1 starter gear can be married to a sub-2400 cruising rpm.
The 2.47 box is usually reserved for road-race applications, that do not spend a lot of time at zero mph, and is really a terrible ratio for quarter mileing, except in certain circumstances.

For Quarter-mileing;Heres how the 2.47/2.66 box plays out;
Say you have a SBM with a 250* cam. That baby is gonna want to rev to make power. The power peak may arrive around 5800/6000, so you might shift it at 6700. Well the 2.66 box has splits of about 71.4% , so when shifting at 6700, the Rs will drop to 6700 x .714 =4786; and the power band will need to be from 4786 to 6700 =1914 . As can be seen the cams LDA will need to be selected to fill that requirement, for best results.
Now let's try it with the close ratio box;
The 2.47 box has splits of about 74.6%. So when shifting at 6700, the Rs will drop to 6700 x .746 = 5000, and the powerband needs to be 6700 - 5000 = 1700. As can be seen, that's 200 rpm better.
Unfortunately, the starting line advantage goes to the 2.66 box with it's approximate 8.5 % more starter gear, requiring one size less rear gear or 8.5% more torque lay-down at the line.
For Eighth mileing, it's a different story
For streeters another story
I got's to toddle off to work now so I'll continue later.