run the smallest yellowtop up front you can and a second larger one in the trunk that 150amp alt will do that fine charging them especially with only a 1000rms system.
Running different batteries isn't advisable according to the dual batt tutorial sticky. It shortens the life of the batts.. The Optima yellow top d34/78 is **** close to the dimensions that you gave. You can get em' at Battermart for about $170 each including shipping. Optima was running a $50 rebate recently too. I got my rebate check in about a month.. It might be over now though.