why do you need so many c-class IPs? most hosts don't even have access to that many c-class differences. and most hosts would definitely want some kind of justification because of the high risk of spam and getting the IP blacklisted.
I know seohosting but they give 5 IPs. I'm affraid but it seems that you will unable to have that with obe web hosting company. I suppose you need to have batch of th companies to have your task done