Read your message on the other thread, too, but thought this one was looking a bit lonely...
I think what you write here is the most important aspect of any used bike - how well it's been looked after. If it has, then you should be fine, in fact this bike is considered a classic in Britain. Worth a bit of money, actually!
There are LOADS of sites on the net about this bike, too. Just enter CB750 on google!
This is a good way of finding out more about the bike. Early Hondas ( and many today ) had problems with cam chain tensioners and there's a chance your bike is fitted with points which you must know how to set if on a trip. I'm pretty sure there are cheap electronic ignition upgrades ( may well have been done ) and if your bike is running well, it must have had the tensioner problem sorted.
Sounds a good deal.Hope so!