@Myopic You have a lot of rust on the suspension arms and frame. If you plan on keeping the car for a long time you may want to consider removing the wheels and lightly sandblasting all the wheel wells and suspension parts. Then get a good coat of urethane black paint covered with a rubberized undercoating.

Do they deice the roads where you live during the winter? That only makes the rust worsen in a hurry.

You have worked so hard on your car to make it look and run right I hate for it to be ruined from rust. Check the bottom of your doors also.