Hi Jerome,
Sorry that the reply responses were a bit slow. You might even have a resolution by now.
There is a lot of info about this subject in this forum and on the internet.
I have purchased DB7 Eibach springs with GAZ shocks, but to be fitted later in the year for my Sportspack 6.0 V12. This normally would make my car lower in the front, but I to ,want to keep the ride height as standard (Sportspack which might be lower and harder than your 4.0).
The write-ups are good with this set-up and our usual Jag parts sellers can supply them (or shop around).
With these DB7 springs you need buy spacer rings, then add or subtract to get your preferred ride height. A lot of work ,as you should really use the correct spring compressor to changeover the rings each time.
Individual standard rings =each thickness is .125”(3.175mm) ,so probably you might need 3-5 to be added each side. Some sellers include a few in a kit.
I avoided the easier option to buy re-tensioned old springs or buy remanufactured springs with the factory tension, because I couldn't convince myself that the ride height would last as long as the originals.
Remember if trying the DB7 springs with spacers ,you only can gage the height when they are tensioned on the car. On the bench the difference cant be judged as the DB7's are thicker and compress in a different way.
As I said, I haven't done this yet, so I will find out later.
Good luck.