The trend I've seen doesn't take a rocket scientist to figure out. Those cars that are limited production increase in value faster. If that "limited production" includes the engine (e.g. Steve's L88 and 427/435 cars), then that appreciation tends to go even faster, probably because that's desired in a sports car (as opposed to a 'rare' paint color, which is probably rare because few people liked it originally
).
All C4s are just starting to come into their own, but of the C4s there are only a handful of 'limited production' models. The Callaway (of course), ZR1, and the LT-4 cars come to mind as about the only limited production C4s with special engines. Of course you can also include the Pace Cars, anniversary editions, CEs, GSs and maybe others, but they often don't include engine changes (some or all of the CEs and GSs may also be LT-4 cars, I don't recall). I think these will increase in value also, but not as fast as the 'engine' cars.
But it all depends on the audience. Many collectors are hung up on "factory original", which doesn't include things like the Aerobody, 100+, or Kool-off options. Those weren't part of the "B2K" option from Chevrolet, so many collectors will shy away from them, while true Callaway fans love those options.
And that's where I think Callaway's have a little bit of an edge. Callaway has become a 'brand' unto itself, and they are clearly not thought of as a mere "tuner" of Corvettes. I think that reputation and history is helping 'Callaway option' values in the open market. One (poor) comparison I can think of is the fender flares that were allegedly included with all L88 cars. They weren't installed, they were delivered in boxes inside the car. Although the flares were included by Chevy back then, today no colletor wants those ON the car - even though many racers installed them right away - because they weren't part of the "factory installed' delivery. If those flares are on the car, then the value tends to be slightly lower because of the body modification (if they're in the boxes IN the car, then the value goes up). On the other hand, there's the Aerobody - clearly not part of the B2K option from Chevrolet and WAY more of a body modification than the L88 flares were), yet the Aerobody cars DO tend to bring a higher price than the non-Aero cars. I think that is due to the 'brand' Callaway.
As for the market fluctuations, it's going to happen as the economy fluctuates. Look at any short-term window of time and you can illustrate an "up" or a "down" trend in the prices. Plot them over the long haul, and I would be willing to bet that the trend is up. To me, buying low and selling high is a much longer term proposition. I've never been able to read the market well enough to make any gains in a car in a short period of time. On my L88, at one point I tried to get out of it too early and could not get more than $20K less than what I paid for it. I wisely decided to hold on for a few more years and ended up tripling my investment. One of the few good car decisions I've made in my life.
In the meantime, drive 'em.
