Simon Brooke wrote:

A 7, 8 or 9 speed chain has the same internal width as a 6 speed and will
work perfectly well. Plenty of six speed blocks still around, ask in
your LBS.

Will it? A 9 speed chain is a lot narrower than 6 speed even if it has the
same pitch. Not saying you are wrong, just that I'd be wary myself.

--
Arthur Clune