How do I keep the stock belt buckle on an aftermarket seat
 

This may be a dumb question, but I was wondering if there is a proper way to mount the stock seat belt buckle to an after market seat bracket, because the nut on the stock seat is welded to the stock bracket. On my last z I just got another nut and bolted it on, but it didn’t allow the buckle to freely move. Just wondering as I am going to put the same seat in my new z and would rather do it correctly this time. Thank you