Darren,
There's a third option you haven't listed, which uses the same carrier bearing mount as you describe, but the bracket mounts to the rear of the crossmember and the bearing assembly hangs down. Let's see if this pic helps.
This is from my '72 C20, and I've found such brackets on other 3/4 tons. I suspect it came with most factory 4 speed and HD drivelines.
I also transplanted this same carrier bearing / driveshaft setup into my son's '69 C10 when we went from a 3 spd (with the slip joint on the output shaft) to the SM465 4spd with a fixed yoke on the output. Gotta have some give in there somewhere...
Hope this helps...SSOW
