I didn't know it at the time, but I took a picture of one of these cars fitted with a six on my 2016 trip, during which I went to Belgium...

There I found in the museum under a building in the town of Stavelot:

[Linked Image from i.postimg.cc]
24-hour race winner. American manufacturers put quite a bit of effort into winning the Spa 24-hours in that era. I thought this must have been a V8 because that's all we saw in Australia, but not so in Europe and the Americas.

Stavelot, of course, is adjacent to the Spa-Francorchamps road circuit.