I'm running a New Process 833 OD in my 57 Plymouth (the MOPAR version).

In the case of the Chrysler 833 ODs there were 2 major variants, with the weaker being the alluminum case and the heavier duty untis being in the cast iron case (mine's cast iron). I have seen a few of the aluminum cases crack when subjected to abuse over the years, and if the chevy unit you picked up is in an aluminum case I would keep an eye on it especially if it's going behind a 454.

The Chevy version of the 833 uses an oddball bolt pattern and takes a special bellhousing and these are not interchangable with the MOPAR cases.

The gear ratios in mine are as advertised in the E Bay add ( 1st-3.09, 2nd-1.67, 3rd-1 to 1, and 4th-.73) which I think was the standard for the majority of the NP OD units.

If you match the final gear ratio in the rear end to how you build the engine these can be a fun transmission. In my case I'm running a Tri-power Hemi (365CI) with a 4.10 gear and 235/70 15 tires. The cam is pretty lumpy resulting a fairly low bottom end torque, but with the 4.10s and 3.09 low it has pretty good manners around town and the .73 OD 4th (it drops engine RPM to the equivelent of a 3.0 rear gear) let's me cruise at about 2800 RPM at 75 MPH. If I had been going for more fuel economy I would have gone with a milder cam and 3.54 gears.

The main down side of these transmissions is that there is a pretty good jump in ratio between 2 and 3rd gear. This can become very noticable in an engine that has a relatively narrow torque curve.