Thanks to everyone from various forums that commented on my boxed-in sides and deeper air dam, I went ahead and tackled the next step: boxing in the bottom of the radiator.
I bought some thin aluminum, a pop rivet gun, and some rivets and went to town! I basically boxed in the bottom the width of the radiatorand sealed off any gaps with some high strength Gorilla duct tape. It's not nearly as "pretty" as some of the fab work I've seen on other cars but I think it'll do the job.
I retained the foam sides of the box that I previously made but somewhat recovered them in the lower bumper opening for better "boxing" and so It'd look a little better LOL!
Now I have to figure out if I "need" an air dam still...whether it be in the stock location (I can re-install the air dam I made) or on the bottom of the bumper, somewhat like the Mach 1 lip.
Here are some pics...It was dark when I finished up so the pics didnt come out as clear as I would've liked, but here you go:
Bottom of the box:
Driver side - inside the lower bumper opening:
Passenger side - inside the lower bumper opening:
Driver side - underneath the car
Passenger side: underneath the car