I've always been a little confused by this topic:
Is what you're talking about truly a "Hydro-Vac", or is it really just a vacuum-assist? My '41 ton and a half has the vacuum assist on it, which is great, but it's not actually a Hydro-vac, as I understand it, because it doesn't actually hold or push any brake fluid. It's simply a mechanical (vacuum) force multiplier for the master cylinder. I am thinking true Hydrovacs came after '46. Not to say one couldn't have been added on post-purchase, of course.
I bring it up mostly because a true Hydro-vac would be probably a couple hundred more to get rebuilt, as they're more complicated. I like the vacuum assist ones, as there's no bleeding necessary, and they're quite simple.
Or at least, that's what I think . . . anyone care to correct me?
-Michael
