In regards to the AC and HP of vehicles, the DMG includes a table on Water and Air vehicles on page 119. However, no analogous table exists for Land Vehicles.
I am aware of the rules on Objects in the DMG on pages 247-8, as referenced by this answer to a similar question. However, the same section also states:
For the purpose of these rules, an object is a discrete, inanimate item like a window, door, sword, book, table, chair, or stone, not a building or a vehicle that is composed of many other objects.
(Emphasis mine)
I am looking for RAW and failing that, RAI backed by evidence and possibly a solution as to how to create these stat blocks.
Best Answer
I don't know of anything that generally describes the AC of land vehicles. But there's this example:
from DDEX3-5, Bane of the Tradeways. It's the only time in WotC materials I remember seeing a land vehicle statted. For reference I've run/played about half of the AL modules (tending toward earlier seasons) and most of the hardcovers (HotDQ, PotA, OotA, CoS, SKT, about half of TftYP, ToA, W:DH, and a little of W:MM).
For comparison, the other (non-land) vehicles I remember statted among those various WotC products:
Taken all together these three vehicles have ACs pretty close to that given for their construction materials in the "Objects" section you already reference. So indications from WotC are to just go with that.