Daniel
If it's of any usefulness check the link below in which it is mentioned
a swedish company that does airport performance analysis for several
aircraft types.
http://www.pprune.org/forums/showthread.php?t=59734
Probably you already know this but just in case you're not aware,
a B767-300 Take-off Weigth (Max) is around 185 tonnes. It could
be a case of, additionally to the extension, also needing to reinforce
the existing runway.
Hope that your airport project of extending the runway will go ahead.
Cheers,
Zerograv