Thanks to everyone for the help!
Thanks to Bob Clayton for the clear explanation and for the suggestion.
I could buy a metal body Johnson guitar with a new cone but some people said me that the Johnson has a good metal body but an horrible neck and keyboard!
Is it right?

No one checked the metal body "Epiphone MD 100"?
Do you think is better than a metal body "Johnson" or "Regal"?

Someone suggested me also an "Amistar"...

Thanks for help, folks!