Try Broader Performance (he used to have them....you have to call). Or FB Performance, they show a 2.75/1.57/1.00 set as an option.
You can also try TCI & Performance Automatic,I was looking at transmissions the other day & saw them listed by someone just can`t remember who.I`m sure most companys that hot rod them can get um.
I've been yoyo'ing back and forth on an AOD/4r70 swap for my car. Let me think on it a bit and I may decide to sell you my new in bag TCI rollerized setup.
I have a 2.92 low set from Broader performance and Dynamic Racing transmission sells both a 2.82 low and a 2.90 ! They are not cheap ! My 2.92 set was new last year so I am sure Jay still sells them, Dynamic still lists there low sets on there web site!
Broader Performance use to give a discount to forum members so if you go that route mention it. They are top notch people and Ford people as well I have bought a transmission from them and a couple valve bodies as well never had a problem with them
One more thing About Broader performance is He is a C4 specialist, Most builders will try to talk you into a turbo 400 or a Glide, They will build a C4 but they don't really like them, Jay knows all the tricks to make the C4 live longer!
The beauty of a c-4 is that a fully rollerized one built right will hold up pretty well,but they absorb less HP than the rest so your car will be faster with them.A turbo 400 is a brute but it takes more power to pull it,a glide does not absorb a lot of power either,but they work better in high HP cars.
It is correct that a C4 can live a while behind some power and torque. Also depends on the weight of the vehicle it's going in, and the type usage it'll see. But even though they have their pro's, they still don't stay together as long as other units do. We were successful in building C4's for a LOOONG time but we weren't making 1,000 hp at 4,000 lbs either. Sometimes when you're making some serious power in a light car, a 3 speed isn't always the best option, but all that is a different story for a different post. And by the way, a glide will work just fine behind a lower powered car too. It's all in the torque converter and trans build, and most people just pick a converter out of a mail order catalog and overbuild the transmission, and then stab it in expecting it to work, and most of the time it disappoints-which is where the 'glide got a bad reputation. A glide going behind a 300 hp drag engine doesn't need 6 or 7 reverse clutches and it doesn't need 6,7,8,9 high clutches-the extra clutches are extra drag. A footbrake 700 hp glide only needs 3 reverse clutches to work, I've used TWO at one point and it worked fine but you had to be careful backing up in that there was to be no throttle input and the idle speed needed to be kept low. There's more ways to free up some drag in a glide which I won't go into, but all done-and done properly-it can (and a lot of times IS) quicker than a 3 speed. I hate putting a GM transmission in a Ford with a passion-but Ford didnt' make a 2 speed automatic that was worth anything from a performance standpoint. Besides, the only thing GM about a well built glide is the case and maybe the high clutch-and even then those are available aftermarket too. The rest might have started life as GM parts but they are modified to the point where there's nothing GM about them. Actually the entire transmission and every single part inside it can be ordered aftermarket. Then you can say you don't have a GM transmission. You have an aftermarket transmission. The TH400 works good behind turbocharged stuff which needs RPM right away without a real loose converter. But it's power hungry. The Rossler 400 works really well and isn't quite as power hungry but it's also a high dollar unit.
In our case we only talking a 300 horsepower stocker will a 2 barrel carburetor that's one reason we want the low first gear
There is a price to pay for the lower first gear as well, and that price is the steep ratio change between gears. Converter can make up for some of it but there again, the converter itself is critical, and you probably already know that. I remember well the days of the old TH700R4's with their HUGE RPM drop between first and second gear.
I have a used set I no longer use. I's fine for a foot break application. I would not use it with a trans break. I used it for years before I switched to a trans break. If your interested let me know. I believe it's 2.88 low and not sure about 2nd. 1.46 maybe. RLB