32-39 gearbox ID

Had an opportunity to dig through a pile of old ford gearboxes yesterday and the only way I know of telling a 37-39 box from a 32-36 box is the 78 thats cast into the rear of the later style case as opposed to the 48 cast into the earlier gear case. What makes them diffrent? Are the 37-39 cases worth dragging home?

 

The 37-39 box has a relief in the front bottom part to clear the large main driven gear on the cluster. So you can mount a 42-48 ge****t.

This the next best combination you can get.

The best is a a 39-49 pickup case with a 42-48 ge****t, it has a thicker bottom under the relief.

 

Thanks for the info. So I'm ***uming there's no asthetic diffrences on the outside of the case that would make IDing the cases easy?

 

i believe all the 78 cases are the thick ones and the 48s being the wimpy ones

 

Cases fall into these sets: '32-34 V8 (B is same box with different bell), '35-36 (Model 48 casting), and 1937 "78" casting, used until 1952 in pickups. All ge****ts can be stuffed into any of the boxes, but some minor trickery in ***embly technique can be necessary with earliest boxes--lack of space affects ***embly work but not running fit.
Biggest difference is at front of bell, and is visible once you have seen the subtle change: The first inch or so of depth of bellhousing just behind flange where engine bolts up is tapered '32-34, from 1935 up it goes back straight for about 3/4". This was changed to accomodate clutches bigger than the early 9". I understand minor grinding allows the bigger clutches to fit easily, but have never confirmed this myself.
All boxes used on production line in '32-48 p***enger cars (except B, whose SN was on the forward bell casting) and commercials 1932-47 will have a serial number stamped above the clutch inspection hole ('32's don't have the hole...) which allows ID of actual model year of manufacture. NEVERNEVER ***ume any early Ford component has what you think it has inside. Ge****ts can be identified in various ways, but the big green book gives specifics if you don't know. And remember late synchro ge****t requires late top with 91A 3" fork.
Serial numbers are here if you need positive ID on a box or frame, but remember not to ***ume that Ford changed types right on time or that a box wasn't restamped. Boxes without numbers are either 1948 and later pickup OR over the counter parts:
http://www.vanpeltsales.com/FH_web/flathead_serialnumbers.htm