I have a '67 Firebird and wonder if I can swap out my rear end for one out of a 1977 TA. I know I've seen this around here somewhere but I can't find it. Too, I've been traveling extensively for the last several years and have probably asked about this before, but I'm about 6 months from retirement and am refocusing my life on my life and not my [censored] job so please, forgive me for repeating myself and thanks in advance for your help!

Dad, congrats on making to retirement. I, myself, have 3 1/2 weeks left and frequently tell people who ask, what are you going to do then?, that I have so much to do that I don't have time for a job anymore.

As to your question...of course you can swap a later assembly in but of course there are adjustments that must be made. Mounting points and spring position have to be modified. Also it is more than likely a different width rear so possible wheel change and back spacing has to be considered. Definitately not a direct bolt in.

The 2nd gen rear will only require having the spring perches repositioned. The width difference is only a quarter inch or so.
I'm retired a couple of years now and loving it. Enjoy!

The strongest BOLT IN rearend for out 1st Gen Firebirds is the Chevy 12 bolt from a 67-69 Camaro, 68 - 71 Nova. The next best is the GM 8.5" 10 bolt from a 72-79 Nova, Ventura, or other GM X bodies. Just be careful from 76 to 79 as they also had a 7.5" which I would stay away from. When I put the 8.5" in my 69 Firebird, I had to shorten my driveshaft one inch, with the 12 bolt I did not have to shorten it, but had to change the rear U-Joint. You can also use the 8.2" rear from the same cars, but not sure if they are as strong as the BOP readend in our cars already, but with upgrades they can be made strong.
This from a Nova site I am on, the dimensions for the 68-79 are the same as for our 1st gens.It shows how to identify the different GM rearends except for the 12 bolt.

https://www.novaresource.org/axle.htm

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I’m curious why are you thinking of swapping?

ANY rear later than 67 that you use to replace the 67 8" will require the drive shaft to be shortened about 1", so measure carefully, the nose sticks out more on the stronger rear ends.

good info here from this site

https://firstgenfirebird.org/f-a-q/rear-end-swap/

congratulations on your retirement! I'm sure that, once retired, I'll wonder how I had time to work! Golf, shooting, FISHING, piano/guitar, and my cars. I cannot wait!

thanks for the information! I appreciate the detail!

because my current unit is the factory, open rear that came with the 326. Given that the 326 has been replaced by a 455, it would be nice to make better use of the power

What gears do you currently have?

On my 69 when I changed to a 12 bolt I did not have to shorten my driveshaft, just change the U-Joint. When I changed the 12 bolt to the 8.5" 10 bolt I had to shorten the driveshaft by 1 inch

Understood. Depending upon the 455 you've built there are several ways to go. If you aren't talking hugely more than stock 455 and have something like a 3.08 already(Firebob's question), you may be able to just install an aftermarket posi unit. Obviously, swapping in a known rear end and making the necessary modifications to spring perches, driveshaft, u-joint, etc. is another viable direction. Lots of choices, that's why the questions.

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Wow, are you sure? I thought the lowest number gear set installed was in the 279 region? Something like that must've been used behind a two sp auto? Regardless, If you're now running a 4speed, gears like that will fry a clutch in short order. My 69 has m20 4speed and 3.23 gear set. I like them but even still I find myself searching for an extra gear when getting on the freeway. I run around 3100rpms at 70 mph.

The 2.56 was fairly common in lower h.p. birds. My '69 350 came with one behind a th350. It even came with posi from the factory.