I assure you, the last thing I want to do is remove the transmission again.
However, I have been making some tiny adjustments and engaging in much contemplation.
I believed I had effectively adjusted the drive shaft angle; but, this is a Falcon, as well as a Ford, and without disparaging Henry, my '62 Ford seems inclined to go to the next junkyard for an extended repose. To provide context, my wife refers to it as "The Falcon from Hell" despite owning it for almost thirteen years and having driven it fewer than 12,000 miles. I often engage in its repair.
Consequently, below are the actions I have undertaken since my last correspondence. Removed the drive shaft and sent it to the individual who rebuilt it for continuity assessment, since I saw some runout. Meanwhile, at the ranch, I performed some shimming and aligned the transmission, differential, and driveshaft to almost a straight line, achieving an angle of 2 degrees and 5 minutes across all three components. Following the reinstallation of the drive shaft, I took it for a test run, and the vibration was less. The sensation was perceptible only after reaching 55 MPH. At speeds of up to 70 MPH, I could alter the frequency by applying pressure and effectively eradicate it by releasing the accelerator or coasting in neutral.
After returning the drive shaft to the rebuilder due to initial inaccuracies, I opted to remove the drive shaft for a thorough inspection. I saw that some balance weights remained on the yoke side in their original positions since I sent it to him for the rebuild. I eliminated them, so also reducing the length.
The vehicle remains elevated on jacks, and I have not yet replaced the drive shaft or conducted a driving test.
I will inform you of the findings upon completion.