alarm ECU clock (if you have one) and stereo will all draw power (even if its off)
on a soak test you should be around 90 milliamps, for a car with a good clip of electronics in it, (the tahoe measured 89ma, with ECU stereo, compass, alarm and immobiliser) so the power drain is minimal, but it is there. a small block will want about 80% charge in the battery to start it properly, so its quite possible to run pretty flat after 6 weeks or so.
once a battery has been run completely flat, its never quite the same, in reality, the best bet is weekly drives, rather than just running on the driveway but thats obviously not an option with the IROC.
If you cant do that, install a cut off switch (the 'red key' type used on drag cars is ideal), they aren't expensive) and isolate the battery completely over winter. Expect the car to feel a little off after the re connection though, as the ECU will need to 're learn' its settings.
the battery itself will hold charge very well unaided if its health - after 6+ weeks the GPz span over like a champ last time I started it (no hint of flatness at all) but of course, a bike has no latent power consumption what so ever.
