Just some cheap observations mostly gleaned from pics of restorations and drawings:
The internal body reinforcement seems pretty simple - including the components for this - simple metalwork indeed.
The front window frame is simple if one keeps it as per the type1 shape or buys a cabriolet body to start with - whaaat...
I see the Heb prototype was with a normal shaped type1 window frame - that suffered from cracking glass - would have to internally braced.
The soft top is no problem either - ditto the dicky type rear seat.
Dash I would leave as a 60 - 69 vintage
The two components that require the most work are the new rear cross section - would have to be hand formed and the decklid.
The decklid would be best fashioned from aluminium.
The side window component are the next tricky area...
But of course none of this would make a Heb at all but a simply a very nice project with an interesting 2 sitzer result.
Turning to other areas of maufacturing:
The other thing I have looked into is Fender Skirts - again very simple panels indeed and with a very simple former are easily made out of aluminium.
Yes I like working with ally mainly from my Landrover rebuild days.
WM