I have no Idea where to start

Agree with the general sentiment in here...

Get/keep it insured, drivable
Fix the little issues
Procure a legitimate factory service manual
Inspect all around under and inside the car (I would pay particular attention to wiring as the factory stuff is literally 50 years old)
Look into parts like electronic ignition upgrade, ammeter bypass if not already done
Go ahead and pull your interior including the carpet out-this will help you build your spreadsheet...it looks like you have a bad front passenger side pan, but look at all the potential areas under the carpet...
Garrett's suggestion above for finding soft metal is a good one...slag hammer works great for that purpose.

I was about to launch into a novel about all the things you might want to start looking into for your desired swap, but you need to figure out "your way." Start perusing the threads about your desired direction, pay attention to the stickies, and read read read. I spend a pretty good bit of time lurking in the resto section because tons of people have already done big metal replacement and documented it very well...the same goes for the small and big block forums, the drivetrain forums, the brake forums, etc etc ad nauseam.

Welcome aboard, I look forward to seeing more about your adventure with your new toy...and I sympathize about the wheels...I am a little curious though-is this still a small bolt pattern car or has it already been swapped?