Gear Vendors question

Back in 2002/2003 ish, I installed a Gvod behind my A833, in a 68 Barracuda.
It only takes a few whacks to the hump, and then the whole entire hump becomes the restriction. Since it still did not fit; From there I had a choice to either cut the hump out with the Tunnel hoop and re-engineer it, or drop the tail of the trans.
I opted for the latter by using a spool mount cross-member, and dropping the spool down as far as it went. For the rest, I dropped the entire cross member a tad, by slotting the holes.
Then I went to the engine, with the idea to lower it, to restore the driveshaft/pinion angle. I saw that my 72/older steering would not work and so I switched to 73 up steering for added clearance. Then I readjusted the engine mounts, to drop it as low as worked without having to smash the TTIs too bad.
Since my car is lowered, the pinion angle wasn't too bad an issue, but yes, I had to work it a bit.
So, what @TrailBeast said is correct and is what most people are gonna have to do.

I went with the GV because I planned to use it as a splitter. With a Commando 4-gear, this gives me EIGHT useable but not sequential gears, which I use in various ways.
Since the Commando runs well this way with 3.23s/3.55s; for a starter-gear of 9.98/10.97, and a hiway gear of 2.52/2.77, this combo works very well for me.
But
If I had an automatic requiring a 3.91 rear gear, I would have installed one of either the A500/A518 units. With a .69 od, you can run just about any rear gear up to about 4.30s with 27" tires.

IMO, if I had an automatic, installing the GVod is at least as much hassle as installing one of the Mopar units, and with the Mopar, you don't have the restrictions associated with the GV, and, you get the .69od verses the .78GVod. That corresponds to about 13% rear gear. And you'll never break the Mopar overdrive.
What using the Mopar unit means, is that you can put Second gear exactly where it needs to be, to max out your street attitude, and Not have to worry about your cruise rpm.
Or in your case, with a 440, you can put Third gear, lol, where you need it to be.

To the guy who asked about changing the A833 A-body m/s ;
Yes the A-body shaft is too short. It is the only part that has to be swapped out tho, as the GVod comes with it's own adapter tail, in aluminum. Unless maybe you have a six-cylinder tail, then you'll need a bigger rear bearing for the GV Adapter unit..
Whereas the B-body has the right M/S already, and yes the cases are the same, except the retainers are different, but that can be changed.
However, swapping mainshafts is easy cuz the whole 4-speed has to come apart anyway, to install the GV tail.
When installing the GVod you will need Chevy Speed-O gears to adapt the unit for the new Driveshaft rpm. There is no work-around for this. GV supplies what ever you need for the First install, but if you swap the rear end, you will need a new matching Chevy gear.
GV offers a deep-sump for their unit, which I opted for, knowing my unit was gonna be working overtime as a splitter, behind my 4-gear.
And, it requires a specific oil, so buy extra.
The driveshaft gets real short with the GV, around 3ft IIRC. This makes setting the pinion angle with the body at the usual HotRod stance, and the engine in the stock location, somewhere between tricky and impossible.
But, if I would have had more money, I would have installed a regular 5-speed manual.
Or, to tell the truth, knowing what I now know, I wouldda just installed less cam, less gear, and more cubes, or just a longer stroke, and still installed the Commando.
For me, it was a fantastic option,
but
if I had an auto, I would swap to a Mopar overdrive, with a well-matched stall. Despite having just four gears, the Torque-Convertor acts like an infinitely variable two-speed (with WOT ratios somewhere between 2.0 and 1.1) and the lock-up is worth near a half a gear. So when you add all that up, it's like having 5.5 gears.