Transient Voltage Protection of an automotive circuit
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.