The Mondeo was a short stroke V6. The Volvos were a T5 stroked down to 2.0 with a mad cutout (9-10k RPM I think). Nissan used 4WD chassis to get the advanced suspension. They stopped a lot of this tinkering a few years ago, more cylinders means lower RPM cap hence the BMW 320s being a high RPM 4 pot and beating the 320i last year soundly.
It's a great sport to watch - I try to get to croft and donington every year, sometimes brands and oulton too.