Can I move my VMAC UNDERHOOD Compressor system from one truck to another?

Consult the Installation Manual (https://www.vmacair.com/support/manuals) for the system you have. 
Enter the model number of the UNDERHOOD^TM system you have in the blank search field (see https://kb.vmacair.com/help/identifying-your-vmac-system to determine model number), choose the Installation Manual from the Manuals column, and refer to the year and model information on the front page of the manual

If no System ID tag is present to identify the system, follow the search under Select Your Product to find the installation manual, or contact VMAC Technical Support for assistance.

If the vehicle you intend to install the UNDERHOOD compressor system in is listed on the front of the Installation Manual then yes, they are compatible.  (e.g. Move a V910010 from a 2012 F-250 to a 2015 F-550).

Any moves outside of this tend to be cost prohibitive, as most components will not be compatible - with the exception of the Air Oil Separator Tank (AOST) and (in some cases) the compressor. The cost to purchase the various individual components (such as the main bracket, tensioners, cooler, hoses, electronic throttle control, etc.) will generally exceed the price of a new system.

Some critical components may be obsolete/no longer available.

Another factor to consider is the labour cost required to remove the components from the old vehicle and return it to original, drivable condition.

In addition, individually purchased components carry only a 1 year parts warranty whereas new complete systems are eligible for full warranty including VMAC’s Lifetime Warranty (Limited) on the air-end.