Offshoreonly.com - Changing Exhaust Tips

I currently have Stainless tips, and I found out that there is not any form of flapper. I just ordered a set of new chrome 4 inch tips from Hardin Marine that have their internal flappers. The problem that I am having, is in regards to the installation of the new tips. The current tips are bolted, (not screwed) in, and I can't find a way to loosen the nuts from the inside of the transom, as the rubber exhaust hose coming from the headers, is a tight fit up against the nut, making me unable to loosen. Any ideas here, other than having to remove the headers? Maybe a special tool that I can buy?? I wish I had taken some pics, but the boat is currently 3 hours away from me, and I am planning on attempting the installation next weekend, but needing an idea as to how to get this job done.

Thanks!