I’ve used just about them all over 50 years, multiple E Types, racing and slaloms etc. The best I think are Spaxx adjustable but I’ve had mine for 25 years and can’t obviously comment on any changes made to them since then. They just seem to work better. They need better bushings than they used (again 25 years ago) - I replaced the stock bushings which had completely deformed 5 years ago with poly from an aftermarket source.
I don’t care for Gaz - two things - the fronts are real wimpy in size, and I’ve long been told that size matters in shocks, but the backs are ok -bigger than the front even though there are 4 in the back. Causes me to believe the fronts are an afterthought to the company. Also mine came plated and have corroded badly - bimetallic action it seems.
When I bought my fhc 5 years ago. It came with Koni Classics - a black painted shock, on the front. They are very impressive - adjustable by the usual Koni method (at least doable on the front as opposed to the rear). Years ago I put orange Koni’s on my '68 ots, front and back, but they were unacceptably hard at the softest settings. That’s an experience others have reported.
So today my coupe has Classic Koni’s up front and Spaxx in the back., and my 68 ots has Spaxx up front and Gaz in the back. I autocross the 68 and the Gaz are easier to adjust than the Spaax - that’s why they are there.
Whatever you buy you need to make sure the rear shocks when fully extended are at least the length of the stock Jaguar shocks.