lucy24 - 9:12 pm on Mar 14, 2013 (gmt 0)
Does one naming format redirect to the other? If so, has G already crawled everything with the /p/ name form? Again if so, all you have to do is remove the "page=" parameter in gwt.
Wait, not quite "all". Depending on your exact redirect configuration, you have to choose between telling it to ignore a particular parameter, or telling it to ignore pages whose URL contains the parameter. Make sure you are clear on the difference.
No matter what you do, URLs containing explicit "index.something" should never occur. Admittedly you don't gain much by redirecting if the whole query string is still there-- but at least you've eliminated one form of duplication.
I don't know whether someone has hard information. I have always assumed that if a search engine comes across /directory/pagename it will put /directory/ alone on its shopping list even if it has never met an explicit link in that form.