Jim - thanks for the detailed explanation - I do appreciate it!

It sounds like the difference between the way Chevrolet engineered my '37 and your '48 is that my features a cross-member for the rear of the transmission - right under the u-joint. It doesn't look like it carried much of the weight - that was handled by the bellhousing supports.

For my project when I removed the bellhousing I needed to cut the transmission X-member for clearance. I stubbed it just in case I figured out a method of attaching to the 700R4 or the adapter:

http://i1098.photobucket.com/albums/g369/J-reb/1937_Chev_Pickup/Trans-Adaptor1_zps876e3fc1.jpg

Then I removed the rear X-member and channeled it so that the 700R4 would fit. Amazingly it still fits up to the original frame mounting points!:

http://i1098.photobucket.com/albums/g369/J-reb/1937_Chev_Pickup/X-Member1_zpse07f1f37.jpg

Here's it all painted and ready for installation:

http://i1098.photobucket.com/albums/g369/J-reb/1937_Chev_Pickup/X-Member2_zpsdbbeb668.jpg

I still need to address the torque issue so I'm going to scrutinize your photos some more!

Everything is different now...