Jason,
Yes, they are both computer altered "Photochops". I have about a dozen such images up on my gallery now, most (like the ones posted on this thread) are the older small black and white ones that I used to do for the NY/CT newsletter. Anyway, the thinking on 1998 midengined Viper was that it would be an actual Le Mans race car, hence it was based on the "then dominant" car at that time, the Porsche GT1. I don't think all the elements, perspective, and that all important proportion works as well on the 1998 car, and perhaps it does look like the Viper parts are slapped on... So you're critique is well founded.
Anyway, I started a thread in General Viper Discussions asking for a Photoshopping-type forum, and I think you have done a lot of this kind of stuff over the years and perhaps it would serve as a useful place for you to post your images. You may want to comment there...