I've recently bought a De Vere 504. I've just purchased the Nikkor EL 150mm f5.6 enlarger lens to print 4x5 negs. For the 504, I have a 39mm threaded lens circular mount fitting, and what looks to be a 49mm one, too.

I know the Nikkor 150mm lens is a 53mm diameter thread. So, my question is:

How do I get the Nikkor enlarger lens onto the 504? Will I need a different lens mount altogether, or, is there an adapter ring of some sort for the 49mm mount I have already?