Generally speaking an IWB holster is accepted as OC - the important point is that the handgun be readily/easily identified as a gun and not hidden from common observation.
Neither your work truck nor a job site are your "place of business;" however, that doesn't create a problem for you with the preemptive laws in both Va and WVa.
Virginia doesn't define open carry specifically, nor legalize it directly. OC is legal because it is not forbidden by law. http://www.opencarry.org/?page_id=310
In West Virginia, one need be aware that certain areas are problematic:
West Virginia is a traditional open carry state but there are some grandfathered local open carry bans not preempted by state law, such as the City of Charleston. There is complete state preemption of all firearms laws, but any local laws passed before preemption remain in effect. http://www.opencarry.org/?page_id=314