After a year of searching, I finally was able to grab a #40399670 bell housing. This is once pretty rare piece. I asked around a few places and the most common reply was 'forget it, you'll never find one'. I was told by a vendor that they knew of someone who paid $800 for one. While I didn't get it free, thankfully I paid nowhere near that.
I'm pretty stoked to have one, it's given me a renewed interest in my truck. Now I can ditch the tractor-like NP435 and install an 833 variant without going to a hydraulic clutch, it's all a bolt-in deal with factory parts.
As most know, the factory never offered an 833 transmission behind a big block in a truck. It is a little odd this part even exists since there was no factory application for it but here it is. Just another one of those weird things I guess.
Anyway, just thought I'd post up some pics of it for posterity.
5.125" bearing retainer opening
This is the part that separates this one from a 'regular' BB truck bell, the little kickout here for the lower right bolt on the 833.
From the side. Someone got a bolt stuck between the pivot boss and the back of the mounting face. Not sure what they were thinking there...
Just for comparison, next to an aluminum BB car bell.
Cool, huh?