my favourite crappy mod is modsgaming.ru (is it even a mod, its actually a mod site but still counts as mod i hate this site anyway)
I don't advocate downloading from sketchy websites, but I will admit I myself have given into temptation, and DL'ed the gold Cadillac Sedan Deville with the gun on the front seat. I think it's a 1984? I like it for its looks, but really a very unadvisable practice. If you like early to mid-80's GM C-Body cars, I really suggest Captain Fido's Old School selections more than futzing with the Cadillac. It's basically in the same family... but if you can find the site without the popups, proceed cautiously.
The dog in the lead car is priceless. Love that dog. I've seen someone use it as their avatar before. What breed is that?