Re: 429 overheating at highway speeds???
Well, I never liked my engines over about 190, I would think that you may have a cooling system issue, but maybe not. That could be a head gasket, radiator cap, timing, carburetion, a lot of possibilities, might be helpful to pull a plug or two and see if it looks lean when heating, and remember that too much timing can give that white plug look too. I had a 400 do this and it needed the timing retarded.