Entry list has just come out, there are 144 entries, covering more than a century of manufacture!
I'm in one of two post-war groups, with a target of 13 laps in 40 minutes (3 mins per lap), which over 3.7 miles works out at an average of about 70 mph. Not really sure how they work out the target, as some other cars on 13 laps are:
Triumph TR2
MGB
Saab 900
MX-5
Clio 172
and a Fiat Panda 1400! Driven by the bloke who is driving this monster:
https://www.youtube.com/watch?v=q7fg3ena88k
There's another Subaru (Forester XT 2.5) but it's in the other post-war group, and he's got to do 15 laps.
Some details on their facebook page here (couldn't work out how to link directly to the post itself).
https://www.facebook.com/VintageSportsCarClub