Amt have re-released the 280 ZX., At 2.8 litres' it's the smallest straight six I can think of.
The triple SU carbs are in the racing version of the Tamiya Jag Mk 2, if you can one, but you know more than I do about resin bits and pieces.
I've seen a letter in a car mag that shows McQueen trying to buy it.
The headed paper was Solar Productions which was his Company IIRC
Nice to see it JC.