Im thinking of a grill block for my 94SL2... I am thinking a little diferent..
If you look at this pic of the OP's car and look at the front end...
Im thinking of filling in that whole front cavaty flush, including those little fake brake ducts.[looks like they do a good job keeping the tire tred cool!!] Mine runs a little hot in the summer, so I am going to leave a small section in the center of the grill. Maybe about 2 foot wide. The rest should clean up the front a lot aero wise, and maybe I can fill in the center in the cold wether. BTW I still have the lower opening. My spoiler was gone, so I just have a small deflector under it that I made of steel, and keeps it cool. I may play around with a bigger deflector/airdam depending on how the grill block works.
you might not have to leave a center section open. i'm running a full grill block on my 99 sc1, but unlike the original post, mine is open on the bottom side. seems to get all the air it needs off the airdam.
I run a 90% grill block, front tray, rear diffuser vortex generators, wheel airdams front and rear and a HAI. I'm planning a bellypan and body pannel gap filling. These planned mods will hopefully improve milage a bit more.