Steve,
I'd say genuine Delco Shock Oil is best.
How much do you need? (If you don't know then check with Gene on this.)
Maybe I can send you some but I don't know if I can ship it or not. Don't know if either USPS, UPS or Federal Express will take it. You do the research on this and let me know how much you need for a one-time service. Or you can use the recommended jack oil. Your call.
No charge other than for the ride.
Best,
Charlie
Oops. After posting I noticed the "modern" word in your post. This oil I have is not modern but some I have still in the Delco can from the old days. Still good as far as I know.