I would look at the 16v systems. Chris Alston Chassis Works has a nice battery box/hold down.

Rock Racing Batteries
http://rockracingbattery.com/home.php?cat=3

XS Power
http://4xspower.com/shop/product-category/14v16v-agm/

Chis Alston
https://www.cachassisworks.com/c-206-battery-boxes.aspx