mono-posto,
I know nothing about Williams 6-wheeler but I bet it was only an experimental model and never raced.
There was another 6-wheeler besides Tyrrell P34 and Williams you just showed us pictures.
That was
March 240 Ford.
It was an experimental model with same two front wheels and four rear wheels configuration like Williams.
Base model was 'March 761', they added extra final drive to the gear box and extra set of wheels at end of the car. All 6 wheels were same small size. It was in late 1976.
Their '77 season new model was called 'March 771' and 240 was just a study.
My magazine I'm looking at right now also has other '77 new F1 models on the same page....Lotus78 Ford, Wolf WR1 Ford, Brabham BT45 Alfa Romeo, Tyrrell Project34 Ford...etc. Black&White photos

[This message has been edited by MN (edited 05-10-2000).]