Bit of nitpicking here (even if it won't bring me any points...), among a few guesses:
4. Lotus Esprit V8
6. Rudolph Spyder by Rudolph Perfect Roadster
9.Gioacchino Acampora Maserati- based one- off "Auge"
10. AMG Mercedes W123 Coupé
11. Dax Kamala
13. Autohaus Nordstadt actually stretched a Golf I to fit over the complete Porsche 928 underpinnings, V8, Transaxle rear drive and all.
15. Strosek- tuned Porsche 911
16. Ferrari 308/ 328 GTB after a Koenig Specials makeover
18. Bertone Pirana (without an h in all sources that I have come across)