My sequence was
-2006 put a TCI2800 'Breakaway' in, piece of crap, no improvement at the strip. But actually improved driving in snow because of its' looseness.
-2007 summer put the 4.56 rear end in so I could rebuild the OEM 3.23 rear end. Blown passenger side carrier bearing.
-2008 August blew the trannys forward sprag racing at the strip.
-2011 May tranny replacement. Drove for 3 years manually shifting because of the blown sprag. 4th gear clutches blew. Picked up a used 4L60E from a member in Indiana. Since tranny was coming out, put in a Yank SS3600. The used tranny was fine and still going strong.
-2011 June put the rebuilt 3.23 rear end back in.
-2018 July Had the back end underneath complete gutted, replacing rusted brake lines, converted everything to AN-3 with SS tubing. Looked at the 4.56 rear end and it said 'put me back in', so I did.
Got a bare housing that I cleaned and POR15'd and gonna build a 4.10 rear end. Got everything I need for it, an un-used Auburn carrier, axles, backing plates. Once the weather warms up, I'll take a look at that project. Hopefully by the fall of 2020 it'll be ready to go in.

 

Thanks Vortec for the mention!

OP as Vortec mentioned feel free to reach out for a recommendation on a converter, it cost nothing for me to go over your combo and provide what i think would be best.
Something to consider while researching these changes with the converter and gearing is how you to plan to drive/use the car. Different driving styles or uses will work better with different setups, so making sure everything is cohesive is key.

 

That moment when you spec out a stall for a 4L60E and then the goals change and you realize that you now must have a 4L80E and another different stall....along with a different trans mount, driveshaft..... yup.

 

A little update. I did indeed find a good deal on a Yank SS4000 to replace mine. I already had the 3.73's and shim kit waiting to be installed so it wouldn't cost much to do it. But then again, if it's only gonna be worth a tenth over my 3.23 is it gonna be worth the time to swap it out. I'll have to debate that one. Hopefully this would put me solidly into the 11's now since I only had it on the track one time since putting it together and only got one decent run as soon as I got there with everything in the back. Ran a 12.13 shifting at 6200. Couldn't get another good run in since I was blowing the tires (Nittos) off every other run I attempted. But now I have some Mickey's to hopefully help with traction along with skinny's and a better converter. Although with the 3200 Midwest converter I did cut a 1.76/60ft time so it did work. Hopefully the trans holds up for a while since a 4l80 is way over my budget. As far as the 10 bolt......guess being a auto it might last for a little while.

 

Yes,the 10 bolt should hold up..
Now the rest is just guesses.
The Mickey Thompsons' alone should take it down to very high elevens.
The 3.73s' might knock a tenth off that but you might not see a top end mph increase.
Going to a Yank 4000 could knock off 4 tenths more.
Recommendation, do the Yank 4000 and hold off with the 3.73s' for now.

 

Thanks, that's exactly what I'm gonna do.

 

I remember when I broke my first stock 10-Bolt differential.
This was in a 1985 Camaro with a massive 190 HP, a T-5 transmission and a 7 and 5/8" 10-Bolt on 10.5" x 28" slicks...
On my first trip to the track with the car; to establish a base-line set of numbers, before starting the power-train swap...

I dumped the clutch at a low 2,500 RPM.
The car went just past the 60' point and the ring gear exploded!

Interestingly enough; I took a Borg-Warner 9-Bolt differential from a 1989 Camaro to replace the 10-Bolt.
I kept the 9-Bolt in the car while I was swapping in the new engine and transmission. I was going to buy a 12-Bolt, but never ended up having to.

I installed at that time a Gen I 350 engine with OEM Vortec heads. I put about 20 hours of work into those heads with a custom cam I spec'd; along with an Edelbrock RPM Air-Gap manifold for Vortec heads, a 4 barrel throttle-body with port injection, and custom headers... IT dyno'd at aprox 630HP at 7,200 RPM.
I had also swap'd in a THM700-R4.
I rebuild the posi-unit for the 9-Bolt with some ARP cap studs, some "secret sauce", some cones, springs and shims from a 2005 GTO, Moser Engineering axles, and a TA Perf. girdle/ diff. cover.

That 9-Bolt differential has held up for the last 16 years along with a progressive 300 nitrous shot on top.
On the engine dyno; that 300 shot made just under 400 HP more at the same 7,200 RPM.

I do not trust the 7 and 1/2" or 7 and 5/8" 10-Bolt units... Even though the (NON-posi) helical gear differentials do hold up much better...
I do trust the 7 and 3/4" 9-Bolt units as well as the 8.2" and 8.5" 10-Bolt units.

 

I'll just hope for the best and see how long she holds up. I agree about the old 8.5" ten bolts. I had one in a "70 Chevelle with a built 427/5000 stall and 4.56 gear and the only thing I did break was a axle. Rest held up great.

 

The 8.5" is a pretty great rear, just about as strong as the 8.875" 12-bolt. I've got one too in my '71 and it's solid.

But I wouldn't worry too much about the 7.5" behind an auto (as long as you can keep wheel hop under control). Sure, some folks have broken them even with the automatic but there are far more examples of them holding up to a bunch of abuse with the auto. Manual is a different story entirely. Here's a great thread with a ton of durability data:

https://ls1tech.com/forums/gears-axl...ock-7-5-a.html

 

Checking it out now, Thanks