UPDATE:

Hey guys. one of my last steps was to use zip-ties to pull the plastic liner firm against the body/pinch-weld. Well, I just did this mod again for a friend this weekend and had a better idea!

Driver Side (& passenger side w/o rear HVAC):
Use a 1/4" drill and just put another plastic rivet on the firewall to pull the liner back and hold it in place Does a much better job than zip ties!

Passenger side:
Since the A/C lines don't allow the use of a rivet, I drilled a hole and used a tree-clip (can get them at Lowe's) in between the HVAC lines and bent pinch weld. Then used a self tapping screw outboard of the pinch weld.

Another trick- A creme-brule torche works great for manipulating/shaping the plastic fender well also!