APU Fitment?

a dynasys only needs 18 1/2 inches

 

Frigette made the one that looked just like the original Peterbilt step but they went out of business.

 

Most will also mount on catwalk. I've seen a Dynasys that way.

 

Not really sure how that would be possible.
There is a large hole in the bottom with a fan to pull hot air out of the unit.
Would likely have to fabricate some sort of upright steel braces to mount to above the catwalk and leave area between frame rails open for airflow.

 

Depending on what you want the apu to do, if you don't need it to keep the engine coolant warm you could get a battery system like the nite system. The 4 batteries for it should fit in the step and then it has a disconnect switch that connects it with the main truck batteries when the engine is running and charging and disconnects them from the main batteries when voltage drops below 12.5 or so. It has A/C and a espar heater and you could then hook a inverter up to that set of batteries so you don't drain your main batteries.

 

Rig master has one designed for catwalk use. http://www.rigmasterpower.com/downloads/RigMaster_MTS-V10_Catwalk-Model.pdf

You can also just remove the ste and fabricate your own. Unfortunelty I think the company that made up went out of business