This first thing you will need is a 168 tooth flywheel. For the bell housing it all depends on how correct you would like things to be. The 1964 409 bell housing can be quite hard to find and expensive but a "621" big block bell housing is much more common, less expensive and will work. For a starter (assuming you are using a 621 bell housing or even the correct 64 409 bell) you will need a block-mounted starter. You can get these at the parts store. You will be getting a starter for a big block (396/427). Just tell them you need a starter for a 1964 Impala with a 409 and 4-speed.
Get all the correct 409 clutch linkage. It will make your life easier. The small block stuff isn't all the same. Show cars has what you need. I believe that the 409 fork for 64 was the same as the small block fork. My parts book seems to confirm that.
Not a bad swap. I've done it before. Just make sure you have everything ahead of time. I didn't and got to learn the hard way!
Best of luck!
Ross