really depends on the shops in your area
try going to a shop and getting an estimate from them, most of the time they'll do a free estimate
from there, price a couple of sets off the internet
if you get any static from the shops about a setup for a six being more expensive than a V8 then i'd go elsewhere
it's the same setup with a couple extra bends, MustangGeezer was once talking about getting a V8 setup and adapting it, dunno if he ever did though