Thanks you, Ivan and Bill, for your feedback!
bill bolton wrote:... but I found that card pretty much killed my Bluetooth connectivity, as I use several Bluetooth connected devices concurrently.

I wouldn't have thought of that, but that would indeed make things rather worse than better. Thanks for mentioning it! - I assume Bluetooth connections were stable again at least when you switched off Wi-Fi separately?
bill bolton wrote:In its place went an Intel 4965AGN plus a Zander BIOS flash, which is all still working very nicely in the T60....
Yes, Intel 4965AGN with a Zender BIOS (... the
ones here (?)) could be an alternative, but unfortunately the driver situation for Intel's whole series of Wi-Fi cards is problematic under Mac OS X, there are simply no working 3945ABG or 4965AGN OS X drivers for connecting to WPA(2)-encrypted WLANs.
bill bolton wrote:It may be a different proposition to find room for an antenna under the plam rest on an X60

Yes, that could become a challenge.

The other way I've now read somewhere here on the forum was to simply
not connect the card's middle connector ...