There is no specific guage to this pattern, what you are looking for is a fairly tight crochet fabric to minimize leaking of the stuffing.
This pattern is good for stash busting, as you will need at least four, colors of yarn. You will need at least half of a 364 yard ball for the trailer, and up half of a 364 yard ball of yarn for the tractor. For the chrome work, you will need possibly a quarter of a 364 yard ball of grey yarn, and just small amounts of white, and black for the windows and tires.
The entire pattern is worked in single crochet, so it is suitable for most skill levels.

NOTE!

Front Window
Row 4 – 8 should read, “repeat row 3, and where it says to break off colour B at the end of row 9, it should read, break off colour B after the 9th stitch on row 8.