Both Excaliburs and Vikings were originally designed to use modified versions of MAC series 44 solenoid valves. These valves are larger and typically low maintenance, however their downside is they require much more battery power to function due to being direct-acting valves. Sometime later AKALMP switched to using Humphrey solenoids instead, which require much less battery power and are typically faster overall, although tend to be a little more demanding in terms of upkeep (however little maintenance is required for them since AKALMP designed the marker to use oil instead of grease).
Regardless of the type of solenoid, the bolt solenoid is located in front with the hammer solenoid in the rear position.
MAC solenoids take up the entire underside of the marker body and cover up most of it. As far as I know, all marker bodies produced until 2004 were milled for MAC solenoids, which look like this:
Markers milled for MAC solenoids required a retrofit milling operation to allow them functionality with Humphrey solenoids. The Humphrey solenoids use special manifold mounts and are boss-milled to seal against the existing air ports directly. Below are pictures of a marker using retrofitted Humphrey solenoids.
Markers produced to accept Humphrey solenoids instead of the older MAC ones use a slightly different milling pattern since they're specifically made to work with the Humphrey manifolds. As a result, these newer markers use slightly different manifold mounts and also a different milling pattern. Below is a picture of a Humphrey solenoid and manifold from a marker milled specifically for Humphrey solenoids.
The above picture shows the solenoid installed on an 04 Viking, but it's similar for 04 Excals.