All I ever use is merged collectors on my stuff. Well, lets put it this way, they could never hurt anything and are very likely to help.
If you need stainless, I would use this Guy. I have purchased from him before and they were as good as anything else I have recieved. If you need mild steel, post or PM me and I will give you another suggestion.

http://cgi.ebay.com/ebaymotors/1-3-4-Sta...eQ5fCarQ5fParts