This project will help keep the heat off your feet when driving your Healey. The description below covers how to build Styrofoam panels and cover them with carpet to add insulation to the box in front of the transmission tunnel. Every little bit help when you are trying to stay cool.
Go to a Home Depot, or the like, and buy a set of 3/4″ steel door insulation panels. They are Styrofoam panels used to insulate overhead doors. The best part is you have enough to do several cars with one kit. Also get a can of spray adhesive. The carpet you use should match the color in your car and also be the type with a very light backing. It must fold and form to the panels.
To keep the contact cement from eating the Styrofoam you can buy the type that has a aluminum foil bonded to one side.
Good luck and try to stay cool!