2.66 low gear vs close ratio

Can't go wrong with the 2.66
However, the 3.09/direct box will let you run one or two rear gears smaller, if you are thinking of any roadtripping.And a stout street360 will hardly feel the 1-2 difference, AND 3.23s with 27 inch tires makes second gear at 2700rpm equals 35mph, the perfect rpm to hammer it.3.55s would up it to3000, and that is not a good cruising rpm.Cruising at 3000 tells the world you are looking for trouble. 2700 says your ready,willing and able, but not actively seeking.Just a little clutch and blast off.
Stout means a short period cam with plenty of compression, to make big low-speed torque.But again, if you intend to go racing,and have a big cam, and are gonna run 4.30s, then it really doesn't matter.
I run 3.55s with the 3.09low, only because I have the GV for an overdrive.For me the minimum cruise rpm is around 2200, where my engine vacuum peaks. So 3.55s is about the minimum gear for making good fuel mileage. If I had less cam, or did not have the GV, I would be running 3.23s. Already tried 'em. Loved 'em. But 3.23s would drop my cruise rpm to 2000@64, which puts my cam back into some degree of reversion, and negatively affects my fuel mileage.

So then the big question to answer, to help decide 3.09/2.66 low is;(actually there are 2 questions),Do you already have a trans and what is your intended usage?
If you already have the 2.66, you ae golden, just go with it.
If you have already purchased a rear gear,just go with it.
If you are a streeter with a 225* or smaller cam, and want to put some highway miles on, then the 3.09low with 3.23s can be a really nice choice.
A little bigger cam will like 3.55s and the 3.09
A little smaller cam will pull 3.55s with the 2.66, or 3.23s with the 3.09; but will likely favor the 3.55s, especially in the higher gears;mostly 4th.
If you are going racing, or for most other applications;it doesn't really matter. If your car really hooks, the 3.09 might get you out of the gate a little quicker.

If you are a streeter I think it would be more important to think about second gear and what speed you will be tooling around at,and get the rear gear that puts your engine in the happy zone, and forget about first for a bit. And that takes us back to paragraph one.