Interesting project but you'd almost certainly need to spring for the plans to get details on the hydraulic seal.
Wonder if a defunct car suspension damper, or Macpherson strut if you wanted to go bigger, could be made to work. Theoretically replacing the valved piston head with a simple solid one and adding suitable hydraulic ports should get you close but I'm sure there is a bit more to it than that.
Major issue for ordinary guy or gal in the shop is needing an external hydraulic pump. Pretty much hafta purchase it and even a hand pump isn't uber cheap. Perhaps an elector-hydraulic power steering pump out of a car would do if you wanted power drive.
Got something similar, but smaller, on the "I'll build it when I need it" list using one of the common "12 ton" puller rams that can be found for £15 (ish) on E-Bay. Short stroke and hafta twiddle a handle but effective.
Having made my version of the Land Rover tool LRT-54-008 to shift the steering ball joints on my P38 earlier this year I'm about half way there. I used the long studs out of a "cheapy-chinee" milling clamp and hold down kit along with the sleeves and plates out of a couple of universal bush removal tool-sets found more or less affordable off E-Bay.
Plan A being to use the universal kits to do the job but was underwhelmed by how well, or rather how badly, the universals fitted. (Objectively using such universal kits was a job for one of the trained octopuses Reliant dealers used to keep for changing Number 3 spark plug and setting distributor points on Regals and Robins.) Normal single Homo Sapiens complement of hands isn't really enough to get everything in, lined up and held in place! Even with really powerful verbals!
So I got making. Could have saved myself over £100 if I'd done that in the first place. If I'd known the sizes in advance of course. But dropping £100 and bit on t'Bay seemed a good bargain for turning the front suspension and steering re-furb into a one weekend "just do it" job.
Ha!
My shop and garage gremlin colonies decided to hold a really big party and invited the whole town to play. Seems like they all came. Bought their friends and relations too. Including cousin Joe G from Australia.
Clive