When you look in the CRD file, you can see that the Viper is in the Street B class. It should show up there. Maybe try to go through the process again. Make sure to uninstall bootfiles, make changes/add entries, add car, and then add bootfiles again.
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The AMS2 mod discord is still a private group. There are things that are worked on in there that some don't feel comfortable being released into the public or shared around while Reiza is still fully working on AMS2. The mods that we have are already a continuous WIP due to Reiza always changing the parameters and physics goal posts so to say. It's a very small group of individuals in there.