Durometer
Do you know the durometer of the material you're moulding out of?
Quick answer is no. I seriously doubt if anyone is going to like the long answer but I will Capitilze my estimate below.
Solid materials are measured in durometer, stiffness or rigidity of foams are measured in Indention Force Deflection (IFD). Most molders do not keep IFD equipment on site as it is too expensive and there other ways around that. (Send it off to a lab is one). IFD is basically the force per surface area required to compress a foam by 25% (There are others but this is probably the most common and the one that I have the most experience with. Note I'm going off my failing poor memory.) In the industry we utilize "Sponge and Rubber Gauges" for manufacturing specs as well as QA/QC.
If I haven't muddied the waters yet.....Hang on I will.
When I worked on the reactions the first thing I wanted was a thicker skin for toughness and durability then I worried about the density and finally the stiffness or IFD (You could call it Durometer).
All that being said, the Durometer Type A from a PTC model 306L reads 42-52 (measurements will vary on what part of the dash you take the reading due to the geometry or surrounding support geometries). I manufacture other products that are a 40 Shore A durometer and they read 45 on this gauge. The original Dash reads 72. (Measurements taken on top horizontal part of dash as if it were mounted).
Therefore I would estimate this to be APPROXIMATELY 45-50 Shore A. The reason I am walking on egg shells here is that theoretically there is no mathematical correlation between IFD, Sponge gauges and Durometer but the mind and hand can tell or do these calculations by feel.
Not to beat a dead horse but the problem with answering your question is one doesn't get the feeling of the IFD because when you compress the part you have more resistance to compression the further you go. It may feel softer for the first instance of compression but you get a feel for the strength as you push harder and harder. The other factor that you have is with an 1/8" thick skin the more you push you are now working on horizontal tensile strength of the skin.
I hope this makes some sense.