Help w Saginaw pwr steering box decode...

[DeadheadNM]

I've got a core Saginaw steering box removed from what I believe was a 72 K20 frame. The box has "7802644L" stamped on it, "*18" stamped just below that, then off to the side a "139" stamped near the time stamp.

I'm considering sending the box for a rebuild and conversion to a quicker ratio. Before doing so, I wanted to confirm it's correct for a 1972 4wd application. Do the above numbers confirm this? I've seen the 780...referenced for 2wd also so am unsure.

Thanks, Pete