Don't take this the wrong way, but you must me doing something wrong. I had an adapter on my Dart with crappy headers for the last ten years and never had a problem changing the filter? Didn't even have to get under the car?!? Lean over the fender, grab the filter with a large pair of sliding pliers and twist off?
Got any pics? My adapter was mounted horizontally with the filter towards the firewall. Seems like a waste of money to me to be adding a filter relocation kit when their are literally tens of thousands of people who have those adapters on their cars and change the oil regularly with no problems.
