Hi Mario
I think that the type of ignition system (eg original, transistorized, aftermarket electronic, etc) as well as year of your car comes into play when choosing the right leads.
I have just fitted an aftermarket 123 distributor together with a Bosch hi-energy red coil on my 1965 230SL. I used the OEM style leads made by Karyln. These have copper cores with Bakelite ends and no resistors.
If you do a forum search on "spark leads" you will get quite a bit of information.
Regards
Franjo