ferrari gt pf special ?

Hi I have owned 1121 GT for many years and have not been able to find the origin of the cars transformation to an covered head light model. It also has two piece front bumper. I raced this car in vintage races at Bridge Hampton, Lime Rock, Louden, and Vermont Hill Climb .
This car was featured on a calendar in the 1980's with a hot air balloon with me and a lovely model and is known as the balloon car .
I know of two other covered head light models , but no one can tell me about the origin of mine . Any help would be appreciated .
thanks lew