Hi folks, thank you for the quick response.
I do have a 79 Puma coupé.
This car is based on a shortened Brasilia floorpan.
Characteristics, compared to a standard beetle:
Ball-joint Type 1 front axle with pre 69 Type 3 brake discs.
Rear swingaxle with Type 3 drum breakes.
The frame head seems to be shorter than Type 1.
The side panels (right expression?) of the frame are wider and differently shaped, especially at the front.
The frame tunnel or center tube is a kind of squarish and lower, rather than high and round.
The rear shocks’ mounts are made of sheetmetal like those of a Type 3.

Questions:
1) Is this floorpan the same as Karmann Ghia Type 14 and / or

VW Type 181?
2) Are there any Brasilias equipped with IRS?
3) Late Karmann Ghias as well as late Type 181 have Independent rear suspension. Is there a chance either to interchange the floorpan or to install IRS into this car?
I know this sounds like some couple of hours of work, but is it possible to get this job done looking like stock VW?
What I am thinking about is simply to have a car that rides, corners, and stops as good as it looks.
Once again, thanks for your input.
Stephan