Hoping to find some experience, or real world suggestions regarding drives seat mount modification, removal, modify seat mounts, add shims if needed, and remount drivers seat back three to four inches. Recent neck surgery and rehab prevents my 6'2" body from bending like it used to. I know reclining the seat back seems like a simple solution, but it does not move the lower part of the seat enough to be helpful.

The car is a pristine 98 with 45,000 miles and all service records current. I hate to trade it for a larger vehicle as none compares to the joy of driving a XJ series. It is the long wheel base and I seldom have anyone in the back seats so rear leg room is not a concern.

Hopefully someone else has modified a seat mount position before and can offer some thoughts before I begin winging it. As the floor plan is molded I am sure I will have to have some type of steel shim crafted for the rear mounts, and possible for the front mounts as well... as well as bending the front seat mount screw holds to accommodate a new angle. Any experience or real world thoughts appreciated. I do not want to give this vehicle up.

Chas256
1998 XJ8 Vanden Plas LWB * 45,000 miles, all records current

 

I think you're on the right track with some brackets. You want to move the seat back so I'd get help removing it as they're fairly awkward and heavy. A couple of connectors to unclip from the cabin loom to seat underneath.

The bolts are a larger torx T55 or similar, can't recall, but they do seize, so flood them all with a release spray before you do anything else, rounding out is real on those bolts. Use the fwd/rvs movement to access.
I'm trying to remember if they pass through the floorpan, the thread ends exposed to atmosphere, in the UK it means they rust. You can spray them from underneath the car

4 lengths of steel plate, bolted at one end to the floor pan, other to the seat. If you fit them to the seat first then align to the floor pan fixing points it's a fairly simple job. Match the seat base angle to the brackets.

 

I think they do. I'm pretty sure I remember a quick wirebrush & spray with WD40 before I took the driver's seat out of my car the first time.