We can yearn for the day when we can pool our money to share a 3D printer that makes metal parts from photographic scans of the originals.  It is probably possible, but not affordable, today.

Maybe it doesn't rotate because the ss "Bolt" is siezed in the aluminum boom plate?

I think the pin has a nut on the backside inside the boom end plate.  To access you have to take the end plate off.  It can likely be freed up by removing the aluminum cap by taking out the small side set screws.  Then dribble vinegar into the cap groove and whack it a few times aa day and dribble more vinegar then apply a propane torch and whack again gently.  Take the cap off and my guess is you'll see the pin is siezed to the aluminum casting but can be freed up with the same technique and then greased so it doesn't sieze again.

Unless of course I've got this all wrong which is possible or I don't understand the problem.

That is correct, thanks Dave

Gary:

Are you sure Lafiell is out of business?, there phones, facebook page (shows some one retiring on the 28th of Jan 2016) and their web site, all are still working. ????

And a bit of thought for any one with issues on finding old parts (Buy a lathe)

if you are building a boat (buy a lathe) it will pay for itself on the parts you will make for the boat. (blocks, shaft, goose neck, etc, etc, etc)

The fitting should be an easy turn with about 6"of  https://www.speedymetals.com/pc-2627-8271-1-516-rd-316-stainless-steel-cold-finished-annealed.aspx

Now it might take 2 to 3 hrs to make it, but the material is only 30 Bucks + shipping. If you are charged for the labor, it may only run you 350.00 +/- to make one.

A side note: when I replaced mine 10 Years back I drilled a hole in the side of the boom and in the outer part of the Al. end block, then used a small drill and tap to install a zirk on the inner part that the above part fits into (Now I grease it with a grease gun) soooooo easy.

I just got through to Lefiel on the phone.