McLaren
Lack of support? Sure that doesn't just depend on the dealer, not the car?
Dodge of Plano is wonderful to me, though they rarely have Vipers in. Same with the Chevrolet dealer here.
But if I go way out of town to another Chevy dealer, nobody really pays me any attention and asks how if I need anything.
Dealer support depends on the dealer and its employees, not the car.
Dealers here in Michigan get Corvettes and Vipers handed to them pretty much whenever they want. I believe Berger is one of the largest Corvette dealers in the state, let alone the country (I want to say the biggest is in California), and even the relatively small dealers around here can get you a Corvette if you really want one. According to our friends at the dealer, each one is allotted a given amount of Corvettes per year, some getting a lot more than others. Most will only get "regular" C6 models, while places liker Berger or Classic have a better chance of getting Z06 models more frequently.
Most dealers around here almost always have a Corvette of some kind on hand. They usually let you get in them, tinker around, and they do allow test drives, although I have yet to get one from a dealer (thats what friends are for).
As for the Viper, well obviously they are a bit more rare and a bit more low-volume than the Corvette. Of the Dodge dealers in town, normally they can get you one if you've got the cash, but normally there is a bit of wait involved. I've only been to the dealer a few times in which they have had a Viper on hand, as you are more likely to find a Ram SRT-10 than the Viper itself. The most I have seen together was indeed two Viper convertibles (this was before the coupe introduction), one black and the other white. Like the Chevrolet dealers, they will let you sit in them, tinker around, etc... But a test drive is pretty much out of the question if you don't have money with you.
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If we want to talk Grattan for a moment, that may turn out to be a very interesting race with the Viper's extra power. Given that GM was supposed to have sorted out the Corvette's suspension, it should be a tad bit easier to control around the uneven surfacing of the course. However, despite how "balanced" the Viper was reported to be, adding an extra 100 BHP is sure to have upset the balance in some way, so it may be a bit harder to handle.
One corner that does come to mind is the tight little twisty just before the (sort) back straight, similar to a carousel at the Nordschleife. Given the tightness of the corner, the Viper would likely fight it just a bit, requiring a larger slow-down, and then given the extra power, may be more likely to oversteer on the way out.
...But really, in-general, the whole back side of Grattan may become even more tricky for the Viper than ever before. Because of the extra power, it will likely become a less "tamed" beast around the track, and given the tighter corners, may have more issues with power on/off situations.
What I would like to see would be the race from the back corner at the bottom of the hill, all the way up to the front straight, and down into turn one. That should be good for 140 MPH before hitting the brakes, so it would be interesting to see who gets there first...
I'm still putting my money in the pockets of the Z06. Lighter, faster, more nimble all makes it seem like the better car at Grattan. Of course the tables could turn at a track like Road America or Silverstone, where longer stretches would presumably give the Viper a slight advantage.