[Otto]

I also have a BMW E36, a '95 325is.

A few thoughts on grill block:

You could remove the chrome plastic surrounding the upper kidney-shaped holes, put black Coroplast between the existing black plastic grills and the metal, for a nearly flush fit. If the flutes in the black Coroplast are vertical, it looks more like a stock BMW.

Black Coroplast also makes a good single piece cover for the lower grill opening. Use the existing black plastic grill to mount it to.

Belly pan of 6mm Coroplast tucks under the bottom of the front bumper cover. Zip tie its trailing edge to the cross bar under the engine. Coroplast sheet could be heated and formed to include wheel spats in the belly pan. Or, make airfoil-shaped spats and wheel fairings out of plastic foam, spray paint black.

Some E36 guys use black plastic lawn or garden edging from Home Depot or other home improvement stores to make chin spoilers that look like stock. This lowers the bottom edge of the bumper cover by ~1.5". Rather than make a new air dam, maybe you could use a heat gun and heat the sides of the existing bumper cover and reshape them by pulling outward so they are as far out as the front tires. This, plus the 1.5" chin spoiler, would give you about the same aerodynamic improvement as a new air dam. Go on Bimmerforums.com in the E36 section for pictures of the plastic chin spoiler.