The opening is 1.5 DIN. There are very few 1.5 DIN units so you'll probably need a single DIN unit with an adapter.
I had my 78 Little Red Express years ago and installed a AM/FM/CB from a car of the same vintage I scored at the junkyard.
There probably isn't one that will provide you a USB port, but more modern radios up through 1999/2000 (year depends on the car line) will physically bolt right in including the AM/FM/CD/cassette units. You do have to rewire a bit to use them.
I can't speak to aftermarket units as they are a target for thieves in my area.
I had my 78 Little Red Express years ago and installed a AM/FM/CB from a car of the same vintage I scored at the junkyard.
There probably isn't one that will provide you a USB port, but more modern radios up through 1999/2000 (year depends on the car line) will physically bolt right in including the AM/FM/CD/cassette units. You do have to rewire a bit to use them.
I can't speak to aftermarket units as they are a target for thieves in my area.