The flicker is caused by the frame rate mismatch between the projector and the video camera. To successfully transfer film to video you need to have control over the speed of the projector. Depending on the shot you may be able to fix it a bit using Auto Color, Auto Levels, or Auto Contrast effects from the Color Correction section. I'd start off with Auto Levels. If that doesn't work try Auto Color. There are Temporal Smoothing settings that may improve things a bit and Auto Color also has Scene detection which may be useful.
Depending on the shot, you may be able to use Color Stabilizer, but if the camera is moving or there's a bunch of movement in the scene you'll have to animate the Black Point and White Point.
I would try Rick's method first; and then for further possibilities you might download a trial of GBdeflicker, it's a plugin for AE developed for time lapsers. I've used it and it's fairly effective, it works by analysing the gamma brightness and algorythymically (sp) smoothing the differences frame-by-frame. It costs money, around $80 last time I checked, but it might help you out.
Rick's suggestion is a good one and might work really well for you, but I've actually had a bit more luck with the Color Stabilizer for 8mm film. The thing to remember with it is to go to a frame without flicker and then press "Set Frame" (Between Reset and About). Try stabilizing Brightness first and see if that works before using Levels or Curves.
you don't need to go highest FPS possible on the camera, you need to choose a multiple of the playback FPS on the projector. But, if your projector doesn't play at constant rate, then you'll need to explore the "fix it in post" options.
8mm is shot and projected at 18 frames per second. The projector has a mechanical speed adjustment that is unreliable at best, normally it is totally unpredictable and varies on its own volition. The pulldown on even the finest 8mm equipment from Canon or Nizo was notoriously sloppy because it really didn't matter much.
If you're shooting an aerial image, the mismatch between the cadences of the shutter in the camera and the shutter in the projector is not great but you will end up with a pattern of blank frames or blank fields when the film is not lit up. You may also get frames of video that have only partial illumination or may have two frames of film exposed on them. These patterns are not regular because of the mechanical nature of the 8mm projector although careful examination of the clip may give you a cadence you can attempt to smooth out.