That is great you are aware of most.
What I said was
'There was an alloy looking 1750 GTV here in Australia by using a GTA as a start point. Technically the Australian modified car could have been a group 5 or 6 GTV 1750 car.'
I could have phrased it a bit better.
There was an alloy looking 1750 GTV that was converted /made up by consuming / using a GTA as a start point, the alloy 1750 GTV looking car was then made to look like a wide bodied GTAm here in Australia, and such a car could have been a Group 5 or 6 car under FIA.
The car you are referring to is the Foley Lightweight, GTA 752561. It never was presented or race-logged as a 1750 GTV in any way whatsoever. In looks it was updated to smooth nose in 1600Junior style, never 1750 in appearance. It also had fibreglass nose, front fenders, doors, boot-lid & rear fenders. It was also fitted with formula-car tubular suspension. It never ran a 1750 engine, but intially a 1900cc 16v then a few other variations.
To draw this car into any conjecture about alloy bodied 1750 GTVs is total fantasy.
I guess your argument that anyone in period COULD have built up just about anything from ordering spare parts is valid, but I think you are grasping at straws suggesting that some elusive 1750s could have been given alloy body parts on the production line. You never know though, perhaps somebody will find one lost in a barn somewhere for 50 years....