Removing large wheels from rear wheelwells

[JMR5]

Hey guys, let me start by apologizing for the stupid question, but it's been a long week and it was 105 degrees today...which means 100+ in my garage. I purchased a 60 GMC 1000 wideside, short bed, big back window truck last month. The prior owner had 20's with 275/45 tires and that just isn't my style, not to mention how hard it was to turn those beasts with manual steering. Anyway, I've got my new tires mounted on steel wheels today and I'm having trouble trying to wedge the old monsters out of the back wheel wells. This is the first truck I've ever owned without leaf spring suspension in the rear and I'm puzzled. On a leaf spring truck I just jack under the frame to clear the tire, but that doesn't work here. On a trailing arm truck like this how do I get the rear suspension to drop down enough to get these huge tires out? Do I need to unhook the coils, shocks and/or pan hard bar? Thanks guys.