What to do with the heater core?

[abadsvt]

I am trying to figure out what to do with the heater core on the firewall. I believe that is what you call it. I plan on doing a LSx conversion and want heat and A/C but wanted to keep the firewall clean. Does anyone know of an aftermarket heater core that is small enough i could put it underneath the dash or anything else that might work? Pictures would be the best along with some info but i will take what i can get. Thanks Josh