Hi Leeroy,
I have not finished my car yet but since nobody else has responded yet perhaps I can tell you what I am intending to do.
1) I will get the headers coated by HPC. Most people confirm that this reduces under bonnet tempreatures considerably.
www.hpcoatings.com
I may even get part of the exhaust coated. There is also a company called Jet Hot which does the same thing but I have heard bad reports and no good reports about them, where as I have only heard good reports about HPC.
2) There seems to be 2 basic types of heat shielding for the engine bay side (aluminium shielding generally goes on the engine bay side as it supposed to reflect heat, I dont think it would be very effective on the interior). There is an adhesive Aluminium shielding and a non sticky matting type. The stick on is thin (looks like thick tinfoil). The non sticky type is thicker and I'm told most people use this and secure it with rivets etc.
3) I figure a good underlay should keep out a fair amount of heat. I used to sell carpet and rubber underlays can be pretty thick ( like the kind they use for Aerobics etc). Or you could use felt underlay (made from wool). Felt is a very good insulator and very fire resistant.
Good question, I hope we get some more ideas.
Regards
Cameron