shock replacement help

[GMCBubba]

hey guys, i tried to do a simple job of replacing the original rear shocks on my 69 3/4 ton leaf spring rear. unfortunately, on the top driver's side, the metal sleeve in the shock is rusted/fused to the post. should i try to cut it off with a grinder so i can replace it, just put the new shock on over the old metal sleeve, or something else that i haven't thought of yet? thanks for the help