A833 OD to early big block?

Hey. So I’ve been trying to search around and see if this is possible. My truck is a ‘81 chassis originally a slant 6 with the a833 overdrive transmission. I bought an early model 383 for the truck. What do I need to bolt the transmission to the motor? I have a regular 4speed a833 big block bell housing lying around. From what I’ve found, it can work but the bell housing either needs to be machined larger or the input shaft on the a833 od needs to be machined down. Is that true? Also what is the best way to tighten up sloppy gears without fully rebuilding the tranny.

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Where are you in Saskatchewan?

The bellhousing will need to be bored out, the input shaft bearing is bigger on the overdrive unit than the standard 4-speed.

What pilot diameter is in the big block bellhousing? What is the casting number on the bellhousing?

Turn your input down to fit, what I assume is a car bellhousing. Or contact brewersperformance.com and buy a new input. I had my turned down for $10 by a guy who had a lathe in his garage.

I highly recommend that you not do this swap.
The overdrive gear in the slanty box is quite fragile. I have blown three of them up , one with just a stock, low-compression 318.
When it blows up, the pieces get into the other gears and take them out..... and then you are walking.
In a truck, the weight is also an issue; as would be a heavy flywheel.
Plus the slanty model has a smaller output shaft. and;
AFAIK your truck requires a truck-specific OD bellhousing, to put the inboard Z-bar pivot, in the right place. With a car-BH, you will have to do some re-engineering, and custom fabrication.
But, making it fit, is the least of your worries.
Cuz;
the 383 is a big-bore short stroke hi-rpm engine, and
that OD box is a low-rpm, very wide-ratio lazy-oaf of a box. The splits are .54-.60-.73. Every gear will require you to rev it higher than you might like to, so that your 383 will pull decently in the next gear.

What that 383 wants, for performance, is a Commando 4-speed, with attached Gear-Vendor over drive, like I have. Splits of .54-.72-.78-.73, Shazzam!!
Sometimes I split-shift the GVod for splits of .78-.80-.78- and by that time I am into 90mph so into overdrive it goes, double shazzam!!!! That will let your 383 do what it was meant to do.
( Just so you know, I have a 68 Barracuda fb, 360, with 3.55s.)