Wow,
You have several things that would concern me.
Batteries: How are they fastened to prevent them tipping over? You isntallation is very dangerous. There are numerous battery threads on how to properly install batteries. For an early car, this is a good one:
duel battries. There are plenty more as well. Some good search terms to use are optima, miata, oddessy, and Sonnenschein.
Rust: Your front suspention attachemnt poitns are directly below the rusted section you show. Often the greater damage is below. Before you attempt to repair what yu show, inspect the under side and be sure your suspension attachment points are STRONG. If they are, you can treat the rust by several means. POR-15 System consists of several treatments in suceesiion. Buy all the products (Metal ready, marine claen, POR-15) and follow the instructions. You can also use rust killers like Naval Jelly, Rust-mort (and others) followed by tradtional priming and paintings.
If they are compromised in any way, you will need to replace the front suspension pan and gas tank support. A good Porsche Shop can do this easily.
Good luck. Let us know what you find.