it is a 92 4x4 with about 172k miles.
because the clutch works fine most of the time although it does have a slight grind going from first to second for the first shift in the morning like the clutch doesn't compress all the way...
Well from my experience your getting close to needing a full clutch service. My 92 made it 200,816 on the factory clutch.... barely.
It started off as slight grinding from 1st to 2nd, before it led up to barely going up a hill in 2nd gear.... 5th was a no-go, clutch slipped horribly bad. I limped it this way for 2 months before I got the money to replace it.
I bought a new ford slave cylinder, just to save myself the agony ( I read a majority of the horror stories of parts store Chinese slave cylinders on this forum) so I hit up fordsvtparts (vendor on here, gives you a discount for being linked to the forum) and I got a new motorcraft slave shipped to my door for $140 (local purchase was $210). It was here in 3 days (ordered on a Friday got it Tuesday)
I went to ebay for my clutch and got a HD setup, it was $75, haggled w/ the guy cause shipping was $10, got it shipped for $75. The clutch is definitely a CLUTCH, took a week to get used to the pressure change. But I have put about 6,200 miles on it since replacement, and still perfectly fine.
Seems like a combination of parts is failing, the bucking and jerking is like the truck is still in gear. Have you tried pumping the clutch a few times before starting it to see if it still does what you describe?
Just a side note if you have a shop or know a buddy who has one, it will make the job 100 times easier than on your back... the PITA bolts were the top 2 on the trans, it requires an insane amount of extensions to get to them.
Might want to consider swapping out the trans mount when doing this job (it's a whopping $20) this was a later found issue that caused some binding on mine.