I’ll bet you just solved my problem. I did, in fact, add the film grain to the track instead of the individual events to save time. I will go back and make this change and let you know if it works.
Another quick question in the meantime: If I changed the project pixel aspect ratio to 1.000 and then cropped each clip to 4:3, is that the same as what you suggested? That is, right clicking and selecting the match output option.