trying to tune my new /6 engine

Hi guys,
I recently dropped in a rebuilt '64 slant 6 engine in my '71 dart. It runs, however does not drive due to the fact that I can't figure out exactly how to tune the newly purchased 390 cfm holley carburetor and timing in harmony. it starts up, but runs rough. I can't seem to get the idle down to the right rpm while keeping the timing correct. Any ideas or suggestions? thanks!