Dave asked me about the type of adapter used on DJ-3As and FJs to connect an automatic transmission (which may have been the Borg Warner model 12 according to David Sapp mentioned in his comment to this post, though I have no documented evidence of this, but it should be out there somewhere). Essentially, a adapter plate is bolted to the back of an L-head/F-head engine, to which the transmission bell housing attaches.
After some searching, Dave spotted the adapter in an FJ supplement book. Here are the pics.
Meanwhile, a discussion from 2012 on the topic of DJ-3A automatic transmissions yielded these pics showing a BW transmission connected to an L-head with a similar looking plate.
As for the rare shifter that’s been captured in some pics, this pic is the best I have (from a DJ-3A automatic). It confirms Barry Goodwin’s comment on another post that the transmission lacked a “Park” feature. Instead, the driver would put it in neutral when parking (and I assume pull the parking brake).
If anyone has a document that confirms it was the M-12 BW transmission that was used, or has more pics or is aware of other useful discussions on this topic, please let me know. There isn’t much info about these setups on the web.
FYI: Based on my research, it appears the Willys Aero cars of the 1950s used a GM Hydramatic rather than a BW transmission.