It looks like some kind of sleeve pressed on to the inner tie rods and the threads are screwed up.
I'm not seeing that??? or is it hidden inside the boot??
I see a pretty standard rack type inner tire rod.....machined from a bar or forging.
Its left the fat original bar size in the middle, machined for the outer thread end size and thread, cut with a little groove for boot retention, and then the end hidden in the boot would be machined to fit the inner pivot ball end that screws to the rack.
If you can't get the info from the builder as to what the original application was or part swap used, then you're left with no alternative but to search the dimesional catalogs for various manufacturers.
Paulz linked you to Moog, should be able to find something there but it might take you a while in research to figure it all out.