11/26/2018  Thomas Kincaid
The Cab-Chassis truck is just that, a Cab set on a Chassis.  Also called a Box truck and Straight truck, it is a very versatile truck style and can be configured in multiple ways.  Look at any new truck dealers lot and you will see new cab-chassis trucks with visible frame rails, waiting to be sold and to have one of a variety of bodies installed:  landscape, wrecker, moving and storage, delivery, tool sales.  Manufacturers like Freightliner, Kenworth, Isuzu Peterbilt, International, GM, Hino, and Ford all offer cab chassis trucks in various lengths and GVWs. 
This article is written with the tool business and new trucks in mind.  We will use the term cab-chassis and box truck interchangeably.  The cab chassis trucks offers the option of an opening cut into the cab and the body, creating a "Walk Thru", about 62" tall, or a "Pass Thru/Crawl Thru", about 44" tall.  The Isuzu is included in this article, although with its tilt cab feature the option of an opening to the rear is not available.  Cab-chassis trucks are becoming more prevalent as Tool Trucks, with Matco Tools and Snap-on Tools designating the Freightliner M2 as the official truck for new franschisees, a switch from the Isuzu NQR and Freightliner MT45 step van respectively.  The GM C5500 was and still is a very popular cab chassis truck but it hasn't been built since 2009, so we won't be discussing it here.
In general Cab-chassis trucks are great for mobile tool sales use.  They offer a comfortable and quiet driver environment, separate from the activity in the rear.  This allows travel between stops to be a time to think about what has happened that day and what is to come, a quiet respite from the days work.   Cab-chassis trucks are also excellent highway performers, good for routes with a large geographic area. 
Benefits of the Cab-Chassis:
*  A Factory engineered quiet comfortable driving experience.  "Power everything" is available.  Heated leather seats are even available!
*  The separate cab is your personal work space.  Customers may look at the front but they typically won't enter your area.
*  Air Ride and Air Brakes are an option (with the exception of the Isuzu).  Smooth ride with Air Ride!
*  Truck dealers stock this style.  Bodies are added later, so you can get a box truck built faster.
*  Body sits on a solid foundation which is quieter and minimizes flexing.
*  The body sits ON the chassis and the Floor is flat so interior layouts are more flexible
*  If you like the truck body/interior but not the truck it sits on, you can move it over to a chassis more to your liking.  I knew a dealer with a 22' Isuzu.  When he found out the hard way - the engine blew - his nearest Isuzu dealer in SD was 200 miles away, he traded the truck in for a big Chevy Kodiak.  LDV moved the body over for him.  He added a walk thru in the process too.
*  Safety - something can come loose on the sales floor and probably not reach you in the drivers seat.
*  The availability of air ride lets you tap into the air source for demo-ing and testing air tools.
*  Tighter turning radius than a step van.
*  If there is no hole cut in the cab, the truck can be repurposed with a new body when it is finished as a Tool Truck
*  Many truck shops are more comfortable and familiar with a cab chassis versus a step van.
*  Taking the truck in for service is easier - just put the panel in place and lock off the back from the cab.
Drawbacks of the Cab-Chassis:
*  Higher price when new
*  Heavier than a comparable step van which means lower legal cargo capacity.
*  The truck body must be longer to accommodate the same inventory as a similar Step Van.  A 20' step van is bigger than a 22' box truck inside.  How?  1.  Body builders measure cab chassis bodies on the Outside.  A 22' body is 22' long on the outside.  A 22' step van has 22' of cargo area on the inside.  2.  A cab chassis side door takes away 24" - 30" of wall space.  3.  There is no additional area up front - above the drivers seat on ceiling and walls, and on the doghouse or engine cover - for display.
*  Higher off the ground than a step van.  It is sometimes 3 - 4 steps up to reach the sales floor.
*  A little body maintenance is required - the body mount U-bolts should be tightened periodically.
There are many more cab-chassis truck options to list here than there are step vans.   The most popular current Tool Truck box trucks are the Freightliner M2, the Kenworth T270 - T300 - T330 series, the Peterbilt 337, and for new tool distributors, the Ford F650 and Isuzu NQR.   Older trucks include the Freightliner FL70, Sterling, and the very popular Chevy and GMC C5500, C6500, and C7500 series.
Considering a Cab Chassis truck for your tool business? Lots of people have done quite well with them. Can't beat them for comfortable ride and security of inventory. The tool business is very local and no two situations are the same. Get the truck style that best suits you and your territory! Is it a Cab Chassis?  Go for it!