Don't use asbestos.
There are a wide variety of safer heat shield products out there.
Truth be told, nothing really works as the problem is a lack of air flow, and too much recirculation of that air flow. Cool air flows in the rear wheel wells, up through the engine compartment and then is drawn out the engine compartment vents. It then flows rearward and a significant portion flows back in at the rear, especially on S1/2 Europas with their open rear panel. TC/S Europas are little better. As shown in other posts, this leads to engine compartment temps much, much higher than the ambient temperature.
The solution?
Good question. Lots of mid-engined cars have this problem. That's why they tend to be festooned with air-flow disrupting scoops. NACA ducts don't flow much. They help but don't even supply enough air for the engine intake.
Honestly, there isn't a good solution. Certainly follow other posts and duct cold air to the engine intake. Never put an oil cooler in the rear area. Don't put temperature sensitive items in the rear luggage area.