For expediency, I used the engine cover and bulkhead the car came with when I bought it. It enclosed the entire middle of the car from just behind the front seats.
Since I installed the transverse 3.8 package, there was a huge amount of empty space back there. Now it’s time to change. The new covers will provide room for groceries and rear seats. The reworked brake lines and water pipes were a first step.
Construction will be plywood panels with metal framing. For fire protection, I’ll face the plywood with sheet metal on the engine side.