hehe, when you say kit car it sounds like you're more interested in a 1:1 scale model.
http://www.locostusa.com/vendors.html
check out some of these links for other Lotus Knock offs. I think many of them use V6's (such as the GM 3.6 or 3.8 litre among others.)
As far as model cars go, I never noticed a large difference in price. Usually supplies are what make the difference. What scale are you looking at?