We (The Rusty Nuts) bought our '87 XJ6 on Thursday. We've been diving into the research and the car and we've discovered a few things.
1) That rattling sound from the top of your engine that doesn't sound too bad and might just be loud injectors is actually loose tappet guides hitting the cam. I'm not sure yet if you can have that sound and last the whole race. I do know there's a fix involving sheet metal screws.
2) Ball joints and tie rod ends are horribly expensive, but one of my teammates tells me there are front-end rebuild kits on eBay pretty cheap.
3) The car weighs somewhere between 3800 and 4900 lbs. We're still not sure, but I did get a weight waiver from HRH Lamm just in case.
4) Everything salvageable in the interior is worth a lot of money, although I don't know why.
5) The intake and exhaust tracts suck. In fact the whole motor is detuned to the point of not having any fun. If you can fab up an intake manifold spacer you might get some more torque. The exhaust collects into a single 2" pipe right out of the manifold and the only o2 sensor is right there. I think the exhaust is gonna suck no matter what.
6) Apparently they only put two different cam sets in the XK motor, and the post '68 cam set is the "hot" set, so no, you can't swap with the earlier cam and get more power. Suck it up and press on.
7) You'll need a long, skinny T-40 torx bit to get the front seat frames out.
8) The rear brakes are inboard, so be sure and bring a tall jack and a nice set of jackstands to the race.
9) The Series 3 is in the back of the XJ6 Haynes manual.
10) Pry up gently on the "added on" back end of the console and you'll find those two last screws.
That's all I can think of right now.