Should be no issues with other vanilla based vehicle mods as shown in previous posts here by arramus, without a log being provided it is difficult to diagnose. I suspect that if you are not seeing the vehicle madness vehicles that the mod has not loaded. Check to see if you have the correct folder in the mods folder as Windows unziping can double nest the folders.
Also you can type version in the F1 console to see whether Vehicle Madness has loaded.
If you check back in this forum thread there is also a link by Black_Wolf for an updated version of Harry's mod.
Regards
Ragsy!!