Hi Scott,
Firstly, I'm pretty sure Benincas GTAM was the same car they ran with carbs for a few year after, & yes, Frank Porter was the main driver for almost all of its life.
I think if your car is only one number different to Bill Magoffin's car ( & his IS a special car) I would start investigating there. Perhaps the might be some similarities in the unusual aspects of the shell. It may be possible that 2 shells were picked & started for the project, Bill's as a full Gp2/C spec car & yours maybe a second that never got that far.
Also, regarding colours, the one my father tested a Talbot Motors was a rather odd shade of pink/maroon/plum? rather than red. I've seen some 105 Berlinas in the same colour & early 1.8 sedans. Certainly not "normal" Alfa Red.
Vin