[Marky Dissod]

Don't worry. headers and exhaust are going on right after the limited slip and 3.55./QUOTE]What's your source for 3.55? Most of us get either 3.42 or 3.73.
Are you getting rid of your ABS? Or did you already get rid of it?

 

[Marky Dissod]

If you prefer ABS remain unmolested, choose between 3.42 or 3.73. Here's how:
The 3.73 vs 3.42 Questionnaire
1. This is my toy, not my daily driver?
Y=3.73 ... or ... N=3.42

2. I'm gonna race, or 'play hard' [for money]?
Y=3.73 ... or ... N=3.42
(also see ?#6, unless you are kidding yourself)

3. I'm gonna tow/haul, or 'work hard' [for money]?
Y=3.73 ... or ... N=3.42

4. I care more about city MpG, less about highway MpG?
Y=3.73 ... or ... N=3.42

5. Many or mostly steep &/or very long hills where I usually drive?
Y=3.73 ... or ... N=3.42

6. I've an extra $600 lying around, just in case I NEED to buy and install a new driveshaft?
Y=3.73 ... or ... N=3.42

7. My valvetrain has [AT LEAST] 1.6 roller rockers AND upgraded valvesprings to support a WOT UpShift of at least 6,000RpM or higher (I've also headers)?
Y=3.73 ... or ... N=3.42
(see ?#1 & ?#2)

If 'N'= 7, you prefer 3.08 / 2.93 / 2.563 - why bother asking?
If 'N'= 4 or 5 or 6 then get 3.42 …
If 'Y'= 4 or 5 or 6 then get 3.73 - and maybe a driveshaft upgrade? Maybe not? Who knows?
If 'Y'= 7 then you NEED 4.11 or more, a definite driveshaft upgrade, a torque converter upgrade, headers, heads, cam …

Upgrade the limited slip differential. If you don't have one, definitely get one.
If you upgrade your torque converter, upgrade your external transmission cooler.

 

[Marky Dissod]

It's my way of reframing the following ideas:
3. Every Impala SS & 9C1 should have come with 3.42 or 3.73, buyer's choice.
2. Every B- & D- car that came with 2.93 3.08 or 3.231 should have come with 3.231 or 3.42.
1. Every B-car that came with 2.563 should have come with 3.08 or 3.231.
(0. Every B-car that came with an L99 4.3L V8 should have come with an L35 4.3L V6.)

 

[Marky Dissod]

Don't forget 2.563.
I'm rounding UP.