dont think about power before you sort the brakes and suspention, pumaspeed do a rear disc convertion but as far as i own its just a recon puma unit, 4x4 cossie brakes up front work well. go for braided line and up rated brake fluid as well. kw coilovers work well with the ka but are expensive so try avo or gas. the rst lump isnt a straight forward swap as a zetec, look for a second hand zvh lump if you still want a blower. a 130bhp zetec will give plenty of go in a little ka