Been fighting a miss since I started the truck back up months ago after having the trans bell housing welded. MSD 6L box It misses ~2000 and under changed the coil got better then would randomly die while cruising, changed to LT1 coil, ran but missed still another side not is that when given 1/2 throttle or more doesn't miss just cruising under 2000. I changed plugs wires even the distributor. All no change I even took the time to do the HEI conversion and it still has the miss. It's the back 3 cylinders if that means anything ALL 3.
1980 D150 SL6
4bbl Holley
Offenhouser intake
Longtubes
.03 over small cam

Is it possible you leaned the engine against the distributor (against fender apron or...) and slightly bent the dist shaft? That can make some cylinders miss and not others. I guess you said you changed the dist. Changed plugs? Sounds like it might be fuel or vacuum leak related if you have changed all those ign parts. Low speed only could be a vacuum leak. Did you try tightening the manifold and carb nuts again?

Lou

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