What about the modern Toyotas that don't have a gauge, just a big red panic light? Is it likely to be to late to save it by the time the light comes on?
Perhaps this discussion should be taken to the tech spam thread?
Buick/Rover 215 (3.5ltr) V8. Fits easily, has been done before so the knowledge is out there, and due to its alloy block weighs little more than the original iron block four cylinder.
You can get away with that sort of thing on a commercial vehicle but I don't believe you can with a passenger car. I'm sure some of the wof mechanics on here will be along to confirm or deny that in due course.
Guy I went to tech with had an early 80s Sigma on cutties. Used to swap back to stock springs for wof day. Reckoned first time he swapped the springs it took him all day but after he'd done it a few times he got down to under two hours.