If you do decide to copy the Jaguar diff mod, remember it is an immensly heavy bit of kit, and pulled the rear of my car down by an extra inch :shock: . It is also slightly larger, although the discs are similar in size, so depending on how well you can mount the diff, it will always hang down low, but on the plus side, it should be good for 300-500bhp depending on the overall weight of the car and tyres used, and comes with lsd and a wide selection of ratios.
Being as you have a v8 shell, it would be possible to build a subframe picking up on the rear diff mounting plate and the front suspension crossmember mounting points and not do any cutting or modifications to the shell, although I cannot gaurantee this as I'm using a 2000 shell.
Here are two articles about the original racer on Rudiger Wicke's site.
p6 racer 1 article
p6 racer 2 article
Reading those articles, it looks like the orginal front suspension was deemed just strong enough by the builders, although there is some scope for upgrading for fast road/racing or just simply the extra loads of fitting wider tyres. The rear would benefit from some extra reinforcing around the top links where they locate on the side of the boot floor, and depending on condition of the elbows, the upper and lower arm mounting points may require some attention. They seem to have a habit of failure from rust, although as it sounds like yours has been dry stored for 25 years, you may not have that issue, but better safe than sorry.
Good luck, and post up some pictures :wink: