Edited a project in 23.976, all the footage was shot at that frame rate. Now we are talking about purchasing some stock footage to use in that project as well.

The stock footage has different frame rates (most clips are either 29.97 and 25 FPS).

I'm assuming I'll need to convert these clips to 23.976 using Compressor or another program.
Will the clips look ok or will the motion look weird due to the conversion?

Any help/workflow tips for a smooth conversion would be greatly appreciated.

Thanks

Whether they look weird, crappy, great, etc. will depend on the individual shot & how it's converted.

Starting off with better quality material will immediately help. Going from 25fps to 23.976 you can simply do a frame to frame conversion by slowing the shot down by (I think) about 4%. There's actually a setting in compressor that will let you do this.

Going from 29.97 to 23.976 is better with interlaced than with progressive material. Either way you'll need to turn on the frame blending and test.