Two options: weatherstripping or garden bed/lawn liner (I think that's what it's called.) The weatherstripping is more rubber like material where as the garden bed liner is a tough rigid plastic.
Use STRONG double sided tape and stick it to a metal strip that can be bent to the desired shape. Fold the top edge of your lip in to make a flat mounting surface, and secure it using the same hardware as your stock lip, including metal strips. That's how I did mine.
I think that rather than bolting his lip up to the stock lip location, viper92086 appears to have stuck it on there with something similar to the STRONG double sided tape that I referred to above. This works too, but raises the lip up above the stock mounting location. This looks fine on darker colored cars, IMO, but messes up the lines on lighter or brightly colored cars. It looks great on his with the black skirts.
viper92086: The look of your car is pure inspiration for my 86.5. Looks freaking awesome!
Collin
