Trailer Life did a feature on Gooseneck converters a few months ago.
All the manufacturer/advertisers were featured of course. No problems noted.
I faced the same problem as my used Dodge had a very robustly installed rotating Ball in the bed.
I've used a Star Performance Gooseneck Adapter hitch for over 3000 miles towing my 13K Lbs Montana without problem. This Adapter has a built in gliding motion and perhaps is better than any advertised in Trailer Life...
http://www.sphitch.com
If this product interests you, email or PM me for more specifics.
Also, consider visiting the Fifth Wheel Forum on RV.net. Currently there are two recent threads about Gooseneck use - one on the second page and a longer more informative one a few pages back, plus a search will find many similar threads over time.
Apparently, Goosenecks do not put enough additional real world stress to cause any more significant failure rate than the many postings here and elsewhere about frame or pinbox failure, flexing, etc using the standard Fifth Wheel hitch. One opinion is the extension of the Pinbox is more of an issue than whatever is between the kingpin and the truck axle...
One significant benefit of a Gooseneck Adapter is the gentle hookup via raising or lowering the trailer onto the ball versus "ramming" a hitch onto the kingpin and assuming you successfully lower the trailer hitch onto the ball, its not going to fall off and land on the truck as apparently happens all too often with normal Fifth Wheel hookups.
I'm a satisfied user.
Good Luck!