I find this interesting... I had looked into the making of a 'custom' coil over kit for my 99 xkr. The main reason is to get rid of the very poor top mounts on out cars.

These guys do a coil over kit which i was almost going to go with:

https://pbbrakes.com/jaguar-xk8-xkr-...nsion-kit.html

but it does not include the rear springs.. that will be where you main trouble spot will be as the shock mounting will have to handle both the damping and also the weight of the car acting on the spring.. What would be the ideal would be to have the rear springs on an adjustable, something like this:

https://www.pmcmotorsport.com/96,rea...-anodized.html

It will adjust the spring... if we can find the right spring size and rate...

I have dampers for the front I can measure for you when I am home next.. the rear I have nothing measurable I'm afraid.

I look forward to seeing what you think about regards to the top mounts at the front...