This is all good to know! Thanks!

The D-II (the older enlarger) is all working but only has 4x5 condenser, holder and lens.
There were some other lenses that came with it but they look crappy. Besides, if doing 4x5, the other lenses won't be used.

The D-2 (the newer enlarger) has the 120 condenser, holder and lens.

The older enlarger has the slot at the top of the lamphouse for filters but the newer enlarger has the rack and pinion height adjustment.
The old one has a good baseboard but the new one has a crappy, plywood baseboard.

The older D-II has been cleaned up but I didn't take it all apart. Only the exterior was cleaned and the optical path. The rest only got the once-over.
The guide rods for the lens carriage could use a good cleaning and lubrication. The rollers and lift mechanisms could use a good looking at.

The newer D-2 will need a good cleaning to get it into operation.

I have been meaning to take the old one apart to give it a full cleaning and the new one will need to be taken, at least, part way apart to clean it. I figure there would be no better time to take them both apart, look to see which parts are the best and put them together into one unit that has everything the way I like.

I think I'll take the old lamphouse with the filter slot, pick the stage that looks the best and mount all that to the rack-and-pinion frame, using the nicer baseboard to hold it all up.

I've got two interchangeable condensers and film holders plus lenses to match. Right there, I have an enlarger for 4x5 and 120 all ready to go.

I'll look for film holders for 35mm and a lens mount for my Nikkors.
Just from looking, I *THINK* the 40 mm will work without modification but just barely. I might be able to get a piece of black Delrin and make a shim ring to raise the lens up by about 1/2 inch. That out to about do it.

If I do all that, I think I should be able to make one Franken-larger that can do everything.

I'll still keep the Beseler but it will be the backup enlarger or the one I teach my nephews on.

P.S. Who ever came up with the hare-brained naming scheme for these enalrgers? Have you ever tried to explain the difference between a "D roman numberal II" and a "D arabic 2"? I guess nobody thought of naming them "D-2.0" and "D-2.1"