e-zilla and BL system - ideas and thoughs?

i can cut out the battery tray a tiny and I could easy mod 7 cells on each side but honestly...

I dont want to blow drive parts all the time I just want it a little faster and longer run times if it were to be a little more efficent with BL.....

I dont need best...i need used and cheap but in good condition :) perhaps a hvmaxx? I dont know....im to new to electric and BL lol