I got that with my two dual-purpose Interstates but now that they've worn out I am looking for something better. I can't use golf cart 6V batteries without some modification of my boxes and cables which I would rather avoid.
The 6V GC2 battery has the same footprint as Grp 24 battery. They are taller. Yes, you would need a small (6") jumper wire between the two 6V batteries. Otherwise, connectivity is the same. There are a lot of good arguments to use 6V batteries in an RV. They are better able to withstand occasional abuse and deliver a lot of capacity for the footprint involved.