Well, if you ever get down to Seattle, let me know. The '68 lives in the Basement of Bad Ideas and is the practice rig from hell these days. You are more than welcome to find out for yourself what it sounds like. The only downside is that it's a little noisy at idle, and it will occasionally sting a little if you are too close to a mic due to some archaic grounding. Neither of those issues is a problem if you aren't trying to sound perfect or sing into a PA.
For what its worth, I had the old one out to play a number of years ago, and got to listen to it side-by-side with an Ampeg head of some kind through an Ampeg 410 cabinet. Neither rig was cranked, and the bass player using the Ampeg was playing a 7ender Jazz. I was playing my 7ender Precision. The near universal consensus was that the Acoustic had a rich, full sound relative to the Ampeg, which sounded a little hoarse and scratchy by comparison. I don't know how else to describe it. But, those old stacks really are all they are cracked up to be. I expect there will still be a few in use 50 years from now when they are pushing 100 years old. After all, who ever would have thought a 50 year old amp would still be not just useful, but preferable?
Needless to say, I have never been much for Ampegs, and probably never will be. The only ones I have ever gotten on with are old fliptops and a friend's B100R combo. They don't have the overbaked sound SVTs have. Even so, I'll stick to solid state Acoustic Control equipment. I know what it does and how to get the sound I want out of it. The downside is that it can be hard to hear onstage unless you are liquefying the audience. Not that I have a moral problem with doing that...
The new 360M is the one I drag around for gigs most of the time, since it can sound like the old one, or it can be just a little drier and more hi-fi. It has a tweeter, so it can get the rockabilly clicky in a way the old one struggles with. If you want snarl and snap, the tweeter helps with that, too.