Nick, if your steering is heavy, first check the idler shaft, make sure it is turning, and fill it with oil.
I am not aware of any version with needle bearings. The pins I used had rubber inside. As far as I can remember, the description “uprated” meant that there was an outer steel sleeve, so you could insert it in your original tie rod end, as opposed to the original design which was a rubber sleeve molded or pressed into the track rod end with the solid steel pin also pressed or molded in, i.e not intended to be repaired, it was sold all as one piece in the old days.
There was an early version with threaded shaft instead of rubber, used only on '48 - mid '50 MkV and 120, see Plate I-12 in the manual. I don’t think any vendor covers that version.
Here is a link to the discussion of 2008.
I also recall that we found the Mk1/Mk2/MkX/420G replacement pin was larger OD than the XK120/MkV replacement.
I looked on Moss and SNG and both have the same thing, with no real useful descriptions. They really ought to get their acts together and provide the customers with something, such as an OD.
If you call them their computer savvy but technically ignorant kids will not know anything that’s not in the computer. But Moss has a tech person who will answer questions like this by email. Maybe the other vendors do as well. If you get in touch with him, try to get him to put the diameters on the web site.
BTW I saw Charles Bishop was part of the 2010 discussion; has anyone heard from Charles lately?