Legally, as long as its done within the confines of an auto-MB enthusiast, and purely for hobby, you're all right.
But it would be different had you with malice constructed a W220 from a W140 with intention to deceit with fraud and misrepresentation blah blah blah with an inducement to lead a third party to think that they paying for a W220 ....
Then in such a case, you're in deep deep *****.
