interesting stats there pager.

the airdam/front spoiler/spook definitely made a difference to my 1200. Not only does it increase high speed stability and 'feel' slightly, but it also made the engine run cooler - even on the street. simple explanation for that is that more air is forced through the radiator rather than passing under the front of the car, and there is a resultant lower pressure behind the airdam (ie under the engine bay) for the hot air in the engine bay to escape to. So a big decrease in front end lift and underbonnent temps. definitely a worthwhile investment for anyone who does track days.

the rear spoiler felt like it made a noticeable difference to my car on the fast bumpy 4th gear sweeper under Dunlop Bridge at Lakeside. The rear was more stable and less affected by the bumps. Before the rear spoiler was fitted it was easy to get sideways there. But this was when I was first starting out - still running on road tyres and didn't really have the suspension sorted back then.

bonnet scoops? not an aerodynamic aid. will only increase turbulance. most will do very little for performance or cooling. scoops are just ricey unless you have a top mount intercooler, or you're very serious about drags or salt flats. for road cars there are much less obtrusive and cheaper ways of getting cold air induction to carbs.

bonnet vents on the other hand can do a useful job of lowering underbonnet temps when fitted properly - particularly on turbo cars. i.e. not like most ricers do fitting them backwards on the front half of the bonnet trying to use them to draw air in! a big ducted vent just behind the radiator can help allow hot air out, but would look out of place on an old car

air flow plates around the radiator are cooling aids. forces air to go through the radiator core rather than escaping via the paths of lower resistance over the rad support panel or through other openings in the panel. not really an aero aid.

lowering? well there's a minor reduction to amount of air passing under the vehicle, but there is also a reduction in the volume under the car for it to pass. I don't think it would be a significant reduction in lift on these old cars. With the shape of the front apron you're still going to get plenty of air being forced under them.

rake will be of no benefit aerodynamically than a level car at the same ride height. the lift effects of air getting forced under the front of the car at higher speeds are felt at the front 1/3rd of the car. its the air getting squashed under the front and being slowed down that creates the high pressure and lift. having the rear slightly higher will not change that at all.

with the 120Y coupe I'm building, I'll definitely be running a front spoiler. No rear spoiler though. with good semi slicks and suspension setup, I doubt a rear spoiler would be any real benefit - just extra weight and a bit of drag. vents and scoops are not allowed in IPRA, but I wouldn't use them even if they were!