I'm a Buick fan, have owned a number of them over the years. (I learned to drive in my parents Electras, my first new car was a '78 Turbo Regal, and currently still own a BCA Senior Gold level '90 Reatta convertible.) I wouldn't bother converting a '99 Riv. You'd spend a huge amount of money, and the results would be dubious. I'd recommend enjoying them as they are.