Call the folks at B&T and they will help you out. Off topic, but what makes you want to go with a traditional mount instead of using the spigot? Just curious.
I am interested to hear the answer, but I suspect the answer is to trade in your current for the lever mount. I am not sure B&T will sell you just the hardware - and I am not sure its just unbolting one and replacing the other.
If you want to see the lever mount broken into major components, you can see at my blog post - maybe it will help figure thing out?
Well since I was able to remove the AICS spigot, I just ordered the ADM 170-S lever, and it bolts right on. If you have the Atlas version that clamps to the rail you have to remove that and add the ADM lever.All in pretty simple.