Scrapiron racing get a fair degree of negative press... I've never bought any of their stuff so I can't comment as to why that might be, but it should definitely make you do some digging on the internet before buying.
AFAIK the only ride difference between a 1992 and a 2007 should be tyre sizes. A 2007 90 has 235/85/16 tyres as an option whereas all 1992 standard tyres were 205/80/16 - a difference of about 2 inches in ride height.
Yes old springs and dampers will drop the ride height a bit too - best replacement would be to fit new ones

IMHO lift kits are only needed if you're going with extreme wheel/tyre mods that will foul the body at full articulation, a body/suspension lift will make the car less stable on the road and without fitting larger tyres won't improve the ground clearance as the diff pans stay at the same height - anything up to a 32 or 33 inch tyre on a stock defender will clear the body and give up to a 2.5 inch extra ground clearance over stock 205/80/16 tyres.
Unless you're planning on competing with the car 235/85's or 265/75's are more than ample for laning or pay and play.
Cheers,