Well, with two days of elbow grease and extreme pressure washing, I've gone from this:

to this:

Pretty good change I would say!
Now I'm having a bit of a debate, that hopefully you'll have some opinion on. The carpet was moldy and nasty, so I took the seats/belts/everything out and ripped it off. Some rust had developed under the wet parts of course, so I scrapped all that off and got a coat of rust-oleum on there, so it looks like this now:

The debate is what to do now? The options I can think of are doing a finish coat of some strong black paint, or attempting to cut my own carpet, or save up and buy a '67 carpet out of a catelogue.
More pics here