Does any one know if a 6 lower can be installed on a NXT? What does fountain do with theres?

I think they do #6 uppers and lowers on the NXT gimbal. Don't know about the #6 lower on the NTX upper.

A #6 drive will bolt to an NXT transom assembly but you need to change the input shaft on the drive to fit the NXT bearing carrier/transmission. I have one if you are interested.

You cannot just swap the lowers and the #6 drive does not have a water pickup built in.