but man I'll take an old honda over an old brit bike anyday, as far as reliability, finding parts and wrenching.
FYI you can get every single part, brand new, for Norton Commandos.
Doesn't matter since they still leak, even with new parts. A 1971 Yellow and black Norton commando made me give up motorcycling for 2 years, before I bought my cb750 and came back to it.
I love birt bikes and now that I don't have to depend on one as my only transportation I would consider owning another, espically a norton. But make no mistake new parts can only get you so far, espically when you have to mix them with old worn outdated parts (ever price out a catalog built norton - $20K easily).
Edit:
On the other side of things I friggin hate lowballers. I posted my friends 78 cb750K for sale on this board and he on craigslist (see it here
http://www.sohc4.us/forums/index.php?topic=13632.0 ). He is asking $1200 for a bike which I think is a decent rider and is in good presentible (non stock but fairly new paint) shape. He just called me to tell me some jackhole kid offered him $650 for it and wouldn't negotiate. I understand these are old bikes and project bikes are a lot cheaper, but this is a running, registered, ready to ride, bike.