........that aircooled heater is as good or better than any other watercooled vehicle.
Don't kid yourself. A Bug will never approach the interior heating of a modern watercooled car.
In order for a Bug to heat well, you have to be making hp. if you're just putting around town, you'll freeze. Get out on the highway, you get some decent heat, but if you slow down for bumper-bumper traffic, all that heat is gone.
If you have a drafty car due to an ill fitting front hood, the heater won't do well then either.
If you are looking for heaterboxes, beware, there are many different types for a Bug. The first ones to stay away from have a smaller outlet tube. Those are for 40hp cars, and they don't fit the tubes in later cars.
Some people have been brainwashed to think that Danish made Dansk brand heaterboxes are the same as genuine VW. Not even close.
The worst heaterboxes are the "lightweight" "racing" heaterboxes. It's just a J-tube inside the shroud. They work well in Mexico, where VW installed them on new Beetles, but they might as well not exist if you have them here.
The Dansk heaterboxes are the same J-tube type as the lightweight ones, but they have some cooling fins cast from alum around them. You can see this casting when you look in the fresh air inlet hole.
The top of the heap are the GENUINE VW heaterboxes. From the outside you might think there's a simple J-tube inside. Not so. The cross section of the pipe that the exhaust gasses flow through is more like a figure 8, but instead of just two bumps, there's at least 4. The purpose is to increase the surface area inside the pipe to draw as much heat out of the exhaust. Then, cast around this is much more effective, deeper cooling fins from aluminum. There's so much aluminum used, it protrudes from the shroud on both ends to maximize the effect. If you want these genuine heaterboxes, you have to hunt the swap meets down south. I've never seen one here, they all rotted out decades ago.