Murphy's Law usually applies. The minute a person dices the junk they had up the back of their garage, someone pops up saying "I would have paid for that".
Stuff that eventually sells:
Original, undented, unplated, unrusted tinware and air cleaner housings
Headers in usable condition
Duraspark units
C4 bells, converters, flexplates and early rear mounts
Undamaged rebuildable carbs
M-code and later heads
Virgin bore seven main blocks
Accessory pulleys and bracketry
That's probably about it in a nutshell.