My 70 Mustang 302 feels like it has a slight miss in it at 65 mph and higher. Car idles great and seems to run great at lower speeds. But when I do get up faster its feels like a small miss in it. The car is stock basically. Still has the original distributor. I'm thinking the distributor magneto may be breaking down. It does not have points in it. its got new plugs but the plugwires do have some age on them. what do ya"ll think ?

 

Could be the wires not sure why you wouldn't notice it till 65. Open the hood in the dark sometime see if you can any wires sparking.