There are definitely two sizes. I got a new one a few years ago from Stoddard, and it was definitely smaller than the original one on my '76. The spring clip on the fan end is smaller as well. I lucked out because I was rebuilding with an earlier fan housing anyway, to get rid of the AIR pump mounts on the top, and the used housing I bought had a torn boot, but with a good clip in it. So I ended up by dumb luck with a complete set of parts.
Can't visualize how you would get yours out of the fan housing from the alternator side, without something tearing or deforming. That's because there's a retainer clip that goes in the boot from the fan side after the boot is installed there. For the same reason, I can't see how you can install a new one from the alternator side- there's no way to put the retainer clip into the boot, except from the fan side, AFTER the hose is installed. Unless you go without the retainer.
Maybe someone can comment on whether you really need that retainer clip or not? Or whether you can preinstall the clip into the hose and then get it into the fan housing?
If you're only changing your alternator, you need to remove the hose end from the alternator, and leave it on the cooling housing.
That may be why yours tore coming off, because the retainer clip was holding it in. And, if you removed yours and tore it, you may have a loose clip under the fan somewhere.
I found one source of new boots, but they're probably the smaller ones, and they don't list the clip. All the clip is is a C-shaped piece of springy steel wire....
http://www.bughaus.com/type222.htmgood luck.... Jim