Hi Gordon,
what you are looking for is a tail section from a 150 L,K,M model.
These models have the bulkhead doubler assembly and the parts you need.
Not sure about the skins but they are most likely just 2024T3 about .40 thick.
The bulkhead and doubler assembly is the hardest to find. Try to buy the Whole tail section. It would be much cheaper than the kit if you find one..
Try
https://www.faethaircraft.com/