Yes 278 ci = 4.5 litres, which is correct.

Some comments:

The rust is a big concern. When there is some to be seen, there is lots more unseen. Together with the mentioned paint issues, you are looking at spending $4,000 - $5,000 on body and paint.

Fuel injection is electronic and problematic. Not many competent mechanics left for this stuff. Parts hard to find and pricey.

Unless you are looking for a challenge, pass it by.