just a hello & some advise please & thanks
 

Well my son purchased a 1978 f250 2wd with a 351m motor 2bbl carb and he wants me to help him restore it. working on carb when we discovered that Ford no longer carries either a idle solenoid or dashpot for this year and so far can not find another source for the parts. Does the vehicle still need these parts or can I run without.

They were mainly emission devices and if not replaced when defective, no big deal.
If the vehicle had A/C the idle solenoid would raise idle rpm to prevent stall due to increased engine load. You can find an idle speed setting that may be slightly faster with no load and still handle the increased load if A/C was turned on.
Some of those solenoids were called anti-dieseling solenoids. What they did was to close the throttle plates on the carb when the ign was shut off so you wouldn't get "run on". The idle speed was jacked up for emission purposes, but if lowered and mixture was adjusted , it would run just fine.