In order to determine if the SolidStep Manual Fold-Down Steps # LC733931 you mentioned will work for your 2018 Bighorn 3160EL, you will need to make two measurements. First take the measurement of the doorway flange, then take a measurement of the distance from the mounting point to the ground to determine the amount of steps you'll need.
The first measurement is known as the "Doorway Width"; and the second measurement is called the "Entry Height".
Using the chart attached, and the... view full answer...