1973 Pontiac Grandville

I’ve owned my black 1973 Pontiac Grandville for more than 20 years. My I first bought it was barely running it looked good and had a nice interior. It had low mileage on the odometer, the pedals had almost no wear, my first mechanic did a compression test which came back good. It’s been a long journey where I spent many years slowly restoring the engine and drivetrain. First thing my original mechanic replaced the original nylon timing gear and water pump. I had to rebuild the transmission, adding a shift kit. My most expensive work was when I replaced all of the lifters and added rolling rockers. I recently received a gut punch that I have undercarriage rust issues, specifically some rust penetration in the passenger floorboard. I need to get a proper rust evaluation from metal working shop. My car starts even after sitting for 2 weeks. Simply press pedal to floor release and turn key it starts on first try after 10-12 seconds, never stalls.