1970 3.2L conversion (rust spot), started project today (worst rust spot) Options

[boxsterfan]

Ok, so I have been doing all of my planning for months now on my /6 conversion. Bought a 1970 1.7L and am going to convert to a 3.2L.

Last night, I started disassembling the car. Took of the rocker panels (PO replaced with plastic/fiberglass ones) and found what appears to be the worst rust spot on the car.

Overall for rust:

1. Front trunk: fine, some minor rust, mostly at seams (as expected), punched at it with a screwdriver and it stayed solid (did not go through). Would give it an B+ for a 30+ year old car.

2. Rear trunk: fine, little rust. Very solid and no rust back by taillights. Punched at it with screwdriver at the few rust spots seen and it is solid. All is minor surface rust. B+ for 30+ year old car.

3. Floor pans: fine, some rust in the seams as expected. No through rust. B+

4. Sail panels: some rust corroding away closest to door side at bottom. Both sides have this. Looks like it can be fixed with fiberglass. B

5. Driver side longs: In reality, very good. Jack port is rusty, but does not go through (does not wiggle all over the place). From the drivers side long back through the rear wheel housing is very solid. A-/B+

6. Battery tray: rusty. needs replaced. Underneath battery tray is very solid (minor surface rust). A-

7. Passenger side longs: The problem area. At the jack port, it is rusted out. Can almost pull jack port out. I would say the hole is about 8 inches long. Starts about 2 inches from rear. The jack point (circle) under the car is solid. The rear wheel area is very solid and was not affected by the rusted battery tray. Passed the screwdriver test. Appears to only be in this "longs" area. Grade of a C.

Basically, the only real trouble looks to be hole in the passenger longs. What are the opinions on getting this fixed?