I'm not sure about the gooseneck. I believe it does not slide but I could be wrong. I don't think the prior owners upgraded any of the standing rigging for improved performance or safety. But I'll check and let you know. Why did you ask? I'm guessing it may have to do with somehow fixing the gooseneck in place if I have the type which slides?
Well I believe that if you go to a rigid vang you will need the gooseneck to be fixed in place, but I did read about a system that does not require that. Garhauer is very good about talking to people, but on the phone. Don't bother emailing, they will just reply telling you to call.
I suggest you call them, explain the situation and see what they suggest, but first find out if your gooseneck slides or is fixed in place.
Installing a rigid vang is less aggravation then installing a rope vang and topping lift, and for $330 the price is right. I have been very happy with the hardware from Garhauer, but I have not bought a rigid vang. That is a next season project.
If you do call, let us know that they say!