From: Leeuwarden, Netherlands
Yeah 1 truck or 1 halftrack for 10 rifle. Or two towed guns per truck/halftrack, or 5 Inf and one towed gun. Carrying capacity is noted somewhere in the unit description, lots of numbers there so you must know where to find it but it's there. (Vic did a hell of a job there, a gazillion numbers per unit and they all make sense) Note that a truck has a "wheeled" form of transport and a halftrack errr "tracked" I think...meaning that in different conditions like mud/forest/hill they have a different movement allowance. Sometimes they can't even enter an hex because of swamp or whatever. Only form of transport that always works is the horse. Horses are the workinghorse of the army so to speak. They can do just about anything, except pull the heavy artillery.
Concerning your HQ question, when the war begins your chain of command is pretty simple. One HQ that pretty soon becomes the Supreme HQ. Most of the stuff you build is there so you can then send it all over the place. Very soon you will also create a few subordinate HQ's to cover all the fronts, so at least four or so to cover all the directions. The more you expand and conquer the more HQ's you want. An HQ has an efficient coverage of about 10-12 hexes wide. 6 hexes with 100% coverage (the farther an unit is away from it's HQ the lesser the bonus it gets from the HQ, that makes sense no? An fighting unit 50 kilometres away from HQ has a hard time getting orders from the brass).
Now say you have taken some territory, or even a continent. Then you face the task of shipping/moving your reinforcements all across the map to your frontline HQ's. So that's why I build sometimes HQ's that are located in ports. Place the SHQ also in a port, then you can send the troops from the SHQ to the HQ located in that port on that continent using cargoships, from that HQ you can then send reinforcements to the frontlines using trains.
Early game you have shortage of everything, middle and especially late game you tend to have too much of everything (if all goes well ) so try to avoid "bloated" HQ's, that is they have too much of everything...they only use up supply. Early game I send everything I have to the SHQ, later on it is possible to send small amounts of troops directly to the frontline HQ's. It's a matter of taste, you'll soon learn what's the most efficient way of doing things.
Now back to your tax returns.