optima battery boxes have been around for a long time. i've had one for 4 years. you can do ebay searches for them.
http://cgi.ebay.com/ebaymotors/Polis...QQcmdZViewItem
some kind of grill plate to cover the rear of the engine bay sounds good if it was like 1/4" aluminum and polished. definitely would need to have large slots or holes so heat can still get thru. would probably need a 2 piece design for the turbo guys.