66? 12 bolt ID help

[closer9]

I've been digging around all morning and can't find a whole lot.

I just picked up a rough 66 SWB yesterday. It has a 12 bolt rear. It's not sitting in a spot where I'd want to pull the diff cover yet. Axle code is HA 07 15 W. It has a shorter panhard rod that seems to mount closer to the diff, with a larger frame bracket compared to my 64 LWB that Grandpa bought new and fairly certain it's all original. Grandpa's 64 also has a 12 bolt (some places say it's 30 spline, others say that didn't start till 65), but a longer panhard with a larger axle bracket.

I found several code charts online, but they all skip 66.

My plan is to rebuild the frame and bed and move my 64 drivetrain, cab and front sheet metal over. Easier than a chop and weld. I just would like to find out as much as I can.

Thanks!