the wheels seem to fill those wider arches pretty good, often you see wide body GT40 with the wheels way to much inside, but maybe that drive's better on the circuit? or regulations? don't know.
I guess you've seen a lot of great cars at such/that event.
It is all down to regulations, the Spa 6 hours will only take cars up to and including 1965. The wider wheels you like are from later years.
Personally, the more I see them the more I like the smaller GT40s.