yeah if you can get a cheap crashed V8 donor car, that'd be the way to go. (as long as the K-frame is not bent) still probably cost as much as selling and getting a V8 instead though.
you'd need K-frame, engine & trans mounts, V8 engine, V8 transmission, (possibly tailshaft), ECU, tacho modification possibly?? V8 springs/shocks for the extra weight, and thats only the start. I'm sure theres a hundred other little things i can't even think of.
its not worth swapping a V6 ecotec for a 5 litre V8. it'd only go slightly quicker. You could easily make a V6 go as hard as a V8 with bolt on mods such as roller rockers, extractors, exhaust and cold air intake. much cheaper and much easier.
if you're still really keen, it would only be worth doing if you were putting in a gen3. but even then, theres probably even more involved, and still probably cheaper to sell and buy an original V8.
hope that helps,
cheers,
James