whoever designed the "armour group" had a problem then - it should be a tank HQ with scout M/C det methinks. Now we have the OOBs fully i our control again, will sort such problems as we find them.
In any case - the "armour command" has nowt to do with rallying (the important function of an HQ) - but does sometimes allow coaching of a unit to throw a better hit roll, if within 3 or so hexes of it - it reverses the low throw, sometimes.
I never bother to buy my HQ any sort of transport, nor convert him to another type. His job is to stay on the baseline where the HQ should be, not to get into combat. If you change to a vehicle - enemy tac air will tend to notice him. As an infantry unit, he can take arty and have a reasonable chance of surviving, and as an HQ element type, he has better arty skills than an ordinary 0 unit, but not those of a full FOO, and if you change him to another infantry type, those skills are lost.
Artillery is found on the artillery menu. Look for "light battery", "medium battery" and "heavy battery" and thier batallions.
hint - off map arty units are all guns, no rifles etc, and on map are individual guns, usually with self defence weapons. The unit will be called something like "84mm Battery" and will have about 30-40 crew serving a platoon/bty of several tubes of off map arty (no personal weaponry), whereas the on-map gun would be called "84mm field gun" or similar and have 8-10 or so crew and personnel serving one (1) on map element.
hint 2 - if you can buy batallions/regiments/brigades etc of the stuff, it is usually off map arty too
Or you could actually have a scratch game (battle generator) and buy things, then see which is which perhaps? - just abandon the scratch game during the deployment after looking at the various purchases you made.
Also - the easy way - see the WinSPWW2 unit classes section of the GG, where the unit classes and capabilities are listed. Learn from that which classes are off-map artillery. If you have not read this section, you wont have a clue what is what, or the capabilities of various unit classes. (I will presume you have played through the tutorial game
and read the tutorial section of the GG alongside that).
cheers
Andy