Those are the standard Ford starting batteries. The house battery (sometimes more than one battery) is generally located near the rear axle but can also be located in a number of places even inside the van. On a 2005 build SMB used a Surepower battery separator to connect or disconnect from the Ford chassis battery system.
IMHO AGM starting
batteries are better than wet cell maintenance free type automotive batteries especially if you have solar. I really like Odyssey batteries for starting batteries but they are higher priced. If you want a traditional battery replacement, the main thing is to replace both with the same make, type, and age when you replace the batteries even if one of the old batteries tests good
Chances are a 2005 would have a Lifeline 4D battery house battery unless the original owner asked for something different.
It's also possible that any of the batteries may have been replaced since 2005. I do prefer Lifeline deep cycle AGM's but am looking looking at Firefly carbon batteries. AGM batteries charge quicker than the wet cell types but the main advantage of an AGM is you don't have to monitor the water level in the battery.
Here is a good link to help explain batteries: