I picked up a Nikon 150mm lens to replace my 135mm on my Omega D4 with a ProLab condenser on the D4 chassis. I just realized why the lens was such a good price. The flange that goes from 50mm to 39mm must have been left on the lens board that the lens came off of.
My question is: I can get a lens board with a 50mm hole and mount the lens that way or would it be wiser to get the adapter so I can use a 39mm lens board that I already have? Would the difference in height matter?
If it were me I would opt for the lens board that will allow mounting of your new lens. Another option is to have your existing lens board drilled to accept the new lens and buy a jam nut for the new lens.
A 50mm hole for a 150mm lens is pretty standard I think. Some might be 42mm but I think that would be only older lenses. So what I'm trying to say is get the 50mm lensboard . Some of the 135mm lens come in 39mm mounts but even in that size some might be bigger then 39mm.
You should be aware that some of the EL-Nikkor 150mm have a 53mm mounting requirement. A 50mm may not work. Better to take some calipers and check before you buy.