probably someones Cash stash once, it was about the era the 1966 decimal currency also flushed a lot of stashed cash out.(70's) elderly people didn't trust banks, kept reserves of cash so it wouldn't effect their pensions,
Paint supplies at hendon will have all the gear you need, the car originally was painted with acrylic.
The paint can be mixed to your code then finely adjusted to match any fading. be prepared though its about $50 per litre.
Best to look at someones car and copy if You Just guess and get it wrong you could do a lot more damage, If You could post what car, what alternator is fitted someone from here will help.
If the panels have been rust converted, sealed with fiberglass matting at the back of the panel then painted how will the rust come back?
Rust needs 3 things 1 steel
2 Oxygen
3 Moisture
take any one of the 3 away and you can't have rust. you should be able to stop moisture and oxygen by the steps taken fingers crossed.
I would use the repo extra cut as it has got no silicons or additive's and can be painted over easy. for badly oxidized areas sand lightly with ultra fine wet and dry sand paper first.