Well that was the most productive night I've had in a long time on the truck, even though it was 2 steps forward, one step back.
I found that I had missed an "oil can" on the firewall which was causing me issues with my filler so I decided to melt off the filler and primer I had already applied so I could heat shrink the affected area. I only wish I remembered to take a before picture.
Oh well. Haha before I did the heat shrink, I had a 1/4" gap in the middle between the straight edge and the firewall. Much better now!
I was also able to get some more sanding on the kick panels done which brings me very close to being done with marglass inside the cab. Good thing too because I'm about out of the stuff.