Stuttering at 1500rpm, then fine...ignition or fuel?

Is it electronic ignition? I just thad the same problem with my 69 340. I put in the Mopar performance electronic distributor and it ran just like you describe.

I removed the distributor and disassembled it and found an extra lock washer was stuck to the magnet on the pick-up. Also.....The silicone block sourrounding the reluctor pick-up was not pushed back far enough onto the mount so the teeth on the reluctor wheel were hitting the block, messing up the gap.

I reassembled it and set the gap at .008 and it runs perfectly now. Smooth from idle right up to 6500 rpm.

The instructions say to set the reluctor gap between .008 and .018, but I found that anything more than .010 causes it to run rough and erratic.

hope this helps.