There's no change interval from Volvo nor is there a really good reason to change yours at only 60K miles (or even 120K). I've seen several 850 MT cars with over 200K miles and original trans fluid. It's synthetic from Volvo and if you still want to do a drain and fill, I'd highly advise getting the same stuff that Volvo recommends as it's obviously good stuff.
I'd call a local dealers parts department first to see if they even stock it because it's doubtfull that they will as most people never ask. They'll probably have to special order some for you.
Now, will another type synthetic be OK? Dunno (reason why I wouldn't gamble).