So I tore down my OM's .357 and .44 and successfully swapped the SBH hammer and trigger from the .357 to the .44 and the standard hammer and trigger from the .44 to the .357.
It involved also swapping out the grip frames, the hammer strut assemblies and the pawls.
The standard hammer had to be fitted to the .357 - it was just barely hitting the bottom of the rear sight. A few careful minutes with a flat needle-file took care of that issue just fine.
Both revolvers lock up tight and appear to index properly.
I am thoroughly pleased with the outcomes!
As a side note, I disassembled the converted 1968 OM .30 carbine BH just to see how the conversion parts
look and function. I saw the "R" stamped on the underside of the cylinder frame where the grip frame covers it. I have no intention of UN-converting that 1968 revolver at this time.