Nice build so far, I am in the same phase right now, ripping out to find rust issues. I used the hammer and screwdriver method as well for the rubber coating on the interior. A good tip that worked for me is to pick up a wide blade razor scrapper. I got mine from Lowe's it was a Kobalt brand, about 3$, it has a razor blade on the end and has a thick sturdy handle that you can hit with a hammer to go at the coating. Congrats on the car, I would say go ahead and remove the bumper shocks if you aren't going to replace the bumper, it looks alot cleaner IMO.