The cam in my bird iYou bi
Sorry you are having all this trouble, these things are hard to diagnose when you aren't there to experience what it's doing. Let me ask a few more questions:
How long has it been doing this? Any change just before it started?
Have you pulled a plug to see if you are actually running lean or rich?
Have you checked your float levels in the carbs?
Have you checked your fuel pressure? (in particular around whatever rpm you are getting the stumble) What kind of fuel pump are you running?
Let's eliminate these and if still no good then move on, I have to tell you though that something doesn't sound right with the timing. I have never ever had a big or small block Mopar that ran best at an initial of 5btc. What's the timing light say all in? (3500+ rpm) Should be somewhere around 36btc but every engine is a little different depending on too many things to list here
s an old Direct Connection Street Hemi grind,280/474.main jets are 65's and ends are 81 passenger side front and rear,83 driver side front and rear with jettable plates,4spd,3.54 dana.runs like a clock.On another note,you don't need to spend $150 for a pair of Promax jettable plates,you can buy a pair of cast jettable plates,same configuration as originals from Quick Fuel for $25 ea,inside the bowl,they both do the same thing and you saved $100 !