I've had both, and i reckon the d21 is at least wider. the later 720 has the same style of torsion front end, and the Z series petrol engine. Subtle differences are the 720 has a standard 2wd gearbox and a remote transfer box, so mounting points would be way off line, and the 720 has an under dash hand brake instead of the usual handbrake on the trans tunnel. that's a start!