I think the OP means the practice of taking an '84-'89 911 and changing the fenders and bumpers to make it resemble a '69-'73 911.
Like this:
AUTOFARM | Autofarm 911 GT 3.4 (2005 build)
On the upside you get the good looks of a longhood, plus the reliability, power, comfort and galvanized body of the Carrera. The downside is that it's never going to be a "real longhood" and you've destroyed a Carrera in the process of making a mongrel.
Cheers
d.