My dads 68 stang has 289 v8, only when the car is idling its like a small miss, I am thinking the plugs are getting old, or fuel filter may need to be replaced.

Any opinions?

 

Could be either of those...
Could be spark plug wires...
Could be distributor cap and/or rotor...
Could be the bearing for the distributor is worn (not likely though)...
Could be a burnt valve...

Start with the easy things, and work from there...

 

yeah do a tune up and pcv valve, fuel filter.......also try dripping some water in the carb to loosen up carbon on the valves rev it up to like 2500 drip water til it seems like it wants to stumble bad quit dripping let it rev up and do it again.do 1 barrel at a time but just the 2 front ones