Electronic – Will a 3D printed ESD dissipative housing prevent spark travelling through air hole to PCB

You may or may not be over thinking this, it depends on what your application is, and if you have to pass any regulatory inspections for a product. The general idea is to shunt the ESD to ground through the chassis and away from your electronics. This depends on if your enclosure is insulated or not. Another thing to keep in mind is you can also have RF running through the shield, and RF should be considered if you need to build a product to pass emissions testing (cables make great antennas, and can even help induct lightning RF onto your board). For now I'll talk about ESD. A good reference for all things ESD and RF is this book Electromagnetic Compatibility Engineering by Henry W. Ott. I'll quote it

So where should cable shields, transient voltage protectors, and I/O filters be connected when the product is in a plastic enclosure? There are three possibilities as follows:

1. To the circuit ground plane (poorest choice)
2. To a separate I/O ground plane as discussed in Sec. 12.4.3
3. To a separate large metal plate added to the bottom of the product (best choice)

In your case if none of the cables go on the outside of a vehicle I wouldn't worry too much about RF. If the cables aren't going to be in contact with people (buried in the dash) I wouldn't worry too much there either. If there going through the middle next to people I would worry. You can think of your vehicle ground like earth ground. The car may collect a charge but it also functions like a faraday cage so everything on the inside will be near 0 (except for something like a seat cover that has been charged up, any metal connected to the chassis will be near 0V (0v being the voltage with respect to the car and not "Earth" ground)).

I've also included an image to suppress ESD in a metal case from the same book:

A 4 - 20mA current loop would normally be sensed, not forced into a controller pin (which is how I am reading your post).

But as Ive read further Im really uncertain whether I can use TVS arrays. Most of these arrays are meant for High speed data lines and not MCU GPIOs.

TVS arrays for high speed data lines are very high performance because they are extremely low capacitance, and they should work fine for MCU pins, but you have the option of using lower speed devices, so the first thing is to define what you need to protect and from what (which is a bit hazy in your question) and then choose an appropriate device.

It is difficult to give further guidance on ESD protection without further details (a system level architecture diagram, or even better, a schematic with the expected sort of interfaces (there is a schematic editor widget in the edit toolbar).

Im using a Can transceiver which isolates the Bus side from the MCU side. Im also using a DC-DC converter to power the 5V devices which isolates up to 1500V which should be enough protection against power surges coming from the 24V battery on the truck?

I do not know what country you are in, but the latest international standard for unswitched vehicle applications is ISO16750, which should give you sufficient guidance on whether you have taken the correct precautions.