Yu cant fit a V8 into a hippo as all the (Land rover) V8's are in line, not transverse without rebuilding the whole drive train and half the bodyshell and brakes to take it.
Dont get a V6 unless you like spending money like water. Either get a TD4 and be happy with it, get a V8 Disco, cos I assume you want comfort - or go buy a lotus7 clone.