I was going to post message on this when I logged on. On a previous post I had this very problem, My 65 289 would idle and accelerate good but at cruising speed it would miss and stutter. I found if I removed the vacuum line to the carb it would run OK. i tried checking the gap on the points and the dist. springs but all seemed good. Last week I got a good deal on a Pertronix kit for 49.95 and a Pertronix coil for 27.95 so I bought and installed them. i noticed the improvement immediately. On the test drive I remembered the the vacuum line and pulled over and connected it to the carb and it ran GREAT! I did not expect it but what the @#$# I am not going to even try to analyze this one.