I just replaced my G24s with a pair of GC2's from Sam's.  They are about an inch taller, and I had to buy new battery boxes, but I found some for $10 each.  The batteries were only $85 each.  I had to reroute some wires to the batteries, but didn't have to change out any wires.
I posted a thread, and got some really good info. From what I learned, the GC2's will last longer, and stand up better to heavy discharge. Below is a link to the thread I started, hopefully it is helpful. 
https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/29421625.cfm