electric revo help

i have a 2.5 revo completely taken apart xcept tranny and elctronics want to convert to electric useing velineon motor and esc and with custom motor mount by tekno rc.was wondering what battery to use lipo or nicd/mh wont most speed and run time possible 3s 20c 8000mah lipo at 11.1 v would work i think or if there was a way to stack /parrellel nicd togetther git same power as lipo with out the lipo hassel i dont mind the weight of battery revo pretty lite help with this would b appreciate help thanx