my 69 340 swinger

Yes, I would change that cam. Go to Comp Cams or Lunati for one of their "Voodoo" grinds. You can still have a choppy idle, BUT will have a modern fast ramp design and can pick something that has MUCH more torque down low...

Then I would change to the 3.91's.

You've already got a really good intake...

The cam and gears will make that 340 COME ALIVE!!!