I thought I could put a jack under the arm and slowly lower the arm down with the jack, but still I'm worried about the spring shooting out. Thanks for you help
That is how you do it. You just have to be careful. There is not that much tension left on the spring when the suspension is in full droop. If you are that nervous you could put a chain around the spring and thru the frame somewhere to keep the spring from going very far. I have done the springs on my '67 Camaro this way a few times--and I used a chain the first time--but found that when the arm went down barely an inch the spring just fell out. I never took the springs out of the '69 Corona I used to own, but I am pretty sure it is the same.