i had 2 international scouts do the same thing, quick fix on them was to put bungi cord on vacuum advance, ran like a charm, both ran fine,one day fired it up and it missed like crazy, 4 of the 8 cyl. were dead. guess it was the bearing inside, never looked further ran fine. with your 235 running push on the side of the distributor and see if it makes a difference, also check rotor, i've seen the end chipped and the tang bent and they run like that.
