I had this erratic shaky idle.
Looked at Service sched it said Valve lash every 15K inspect/adjust.
Set piston1 to TDC 0degrees (check on dist cap)
remove valve cover.
Check valve 1 & 2, 4, 6 (numbered from front to back)
rotate engine 360 degrees
then check 3, 5, 7 & 8
all of them were too tight since the valvejob so I had lash adjusted @ .007 intake and .011 exh COLD
slapped everything back
fired her - no spark - oops forgot the dist cap
fired her
what the heck is that sound?
oh chit i forgot the rachet on the crank pulley

Fired her up again, warmed up
idles WAAYYY quieter and TONS smoother.
no more shakes!!!
I enjoy driving my truck that much more!!!

This is part of the reason I prefer working on an old truck.
ALways something to do, so i never get bored of it.
Next I'll attack the front end alignment with a set of 14" alloys and tires I found for CHEAP.