Hawkeye seats into a classic
 

How much of a pain in the arse is this?

front and rear ideally.

chars

Fronts dead easy, but they ride substantially higher, and may don't like it.

Rears not sure.

Yep both fit, The rears also sit a little higher so you may need to spray the top of the rear seat foam on the back to disguise it, so it's not seen from the rear window if your looking in.