You should be able to take the four nuts on the u-bolts off completely and then lower the rear differential slowly (with the cars frame on jack stands)and it should release the pressure on the upper leaves. You will have to have a spring spreader as mentioned in removal of the lower leaf. If I had my rear spring out I would definitely refurb it with disassembly, re arch and graphite paint. I just did my front and rear and am very satisfied with the results. There are a few videos you can watch on YouTube as to how, it’s not rocket science and it would be very hard to over do it in the rearching imo. Rumor has it that the allies dropped two model a rear springs from aircraft during WW2, one over Hiroshima and one over Nagasaki.

. Seriously they are dangerous but once you understand the pressure and how it releases it’s easier to deal with it.