Alright lesse... start from the start.
As you know you need to be a member of a CAMS afiliated car club, which is easy, there are hundreds of them... check CAMS web site.
Then you need a CAMS level 2S license or better which I presume you already have since you've taken the 690SEL out at OP you'd have needed something like that.
Now, armed with those two items you can then start inviting yourself to any club level event that the various clubs in NSW are running. No club has the finances to run 12+ events a year so they typically run 4-5 events and invite members from other clubs to join in.
Where I am, in Victoria, I keep and eye on the Ford Four Car club (
www.ffcc.asn.au ) and Marque Car Club (
www.msca.com.au ) which have a calendar of events for the year and I just invite myself to whichever ones I feel like attending. It should be easy to find similar clubs in NSW.
I race at the 4 major tracks in Victoria: Calder, Sandown, Philip Is. and Winton, and also at the autocross facility at Avalon. Once or twice a year the other two lads join me at either Sandown or Winton.
Now to answer your questions:
Remove all bumpers (front and rear)?
Yes you can.
Can I gut the doors (except drivers side) and weld the back ones to the body (leaving nothing but a shell with some perspex instead of glass)?
Yes you can, but people rarely do this, you still need to keep the impact intrusion bar inside the door. It also severely restricts working in the rear compartment of the cabin but its your call. If you weld all 4 doors Nascar style then you need window nets on the front doors.
Can I gut the whole interior?
Yes you can. The less in there the better. If you have the $ you can even remove the whole dash and heater, console, the lot. Ideally all you want in the cabin are the seat and harness, sports steering wheel, pedals and gauges. And your fire extinguisher. Some people even make an alloy instrument binnacle and populate it with autometer gauges, if thats your thing.
What sort of modifications am I NOT allowed?
No nitrous. Slick tyres are allowed but the car has to have a roll cage, but with the semi-slick tyres we use (Yokohama A032/A048 family) are allowed without a roll cage.
Your tyres must remain within the confines of the bodywork (so if you are fitting ultra deep dish wheels then you need to flare the guards). No wheel spacers allowed.
Any other questions just ask.
I.