About the only manufacturer left is Revell-Monogram. They aren't bad, certainly a lot better than AMT's offerings.
If you want the older race cars, Polar Lights does some of those. I've not built any of them yet but they look decent.
I'll say one thing though, you'll have a very colourful collection!
A building tip, the front grille. On some cars it is a separate item and they usually give you a decal for that as well. Install the grille and file it flat and fill any gaps. Once it's all smooth, you can apply the decal grille. Helps it look much better.
Good luck with your collection!