I got back from vacation, and I managed to get the floor and the rear of the firewall painted. First, I needed to finish filling some rust pits. The storage area under the front seat and the rear footwell were rather pitted, and about two years ago I sandblasting and primed the floor and filled most of the pitting. This week I finally finished the job.
After finishing the filler work, I applied the finish coat, which is the same that I used to paint the underside of the body and the front of the firewall: A semi-gloss maroon color.
I also noticed a a place on the roof where the contour wasn’t quite right. It became noticeable because the roof (and the entire car) had a smooth-uniform layer of light-colored primer-surfacer. So I had to sand off the primer, apply some more body filler, smooth it to the correct contour, and re-apply the filler-surfacer.