c800 rear light on vl800

I prefer the c800 rear light. Is it a direct bolt on to the 04 vl800?

Direct bolt on no, minimal effort yes.

It could be made to fit but it would mean cutting a hole in your fender and manufacturing some sort of brace for the inside of the fender, it's a different fender and brace on 09 and later models and the holes are in completely different places, there's also a large recess in the fender on later models to accommodate the inside of the LED light which the earlier models don't have.