wmark,
Hello from Ft. Collins! How much snow you got down there? We were closed yesterday and are spending today digging out. Oh yeah, shocks.
The inner workings of your lever shocks are entirely made of metal and as such won't suffer from any oil that doesn't eat steel! The seal(s) on the output shaft(s) are rubber and are notoriously unable to stand up to much more than air. The safe bet is the correct shock oil, of course, but if you need to fill the shocks, the seals are probably already compromised. So, I'm not sure it matters all that much what you use. I hesitate to make any specific reccomendation though as I don't know who rebuilt the shocks that are on your machine now or what material they used for seals. In the replacement parts industry these specs tend to change all the time and are difficult to nail down.
I could give you all kinds of annecdotes about these shocks and the desparate measures I remember guys taking to keep them full when I was younger, including a remote resevoir one guy hooked up to the fronts on his MGA and a friend of mine who used progressively thicker and thicker lubricants, thinking the shocks would not only leak less but would stiffen up and become "high performance". All went fairly well till he opted for STP, which took him hours and hours to install and became virtually solid the first night the temperature dipped rather low. He then had, in effect, no front suspension at all. When he went up a drive entrance one wheel would actually come off the ground! This taught me all I needed to know about STP and I never put any more of it in my engines. It also taught him how to order new shocks.
None of this helps you at all, but I love remembering the good ole days.... Look, if your seals are visibly leaking use any light oil. It's too late to save the seals. If they aren't leaking, order the right stuff from Moss or whomever. Beyond that, I guess you could write to the various shock rebuilders and ask them what the seals are made from. My guess is Doublemint.....
Motorbill
From Lola to Land Rover, If it's British and has wheels, it's likely I've bloodied me knuckles thereupon