I have changed plugs from both the top and bottom and will do it again soon when I get my iridite plugs. If you have access to a lift or a good set of ramps and stock manifolds, the easiest way to change plugs is from under the car. I have headers on both of my SCs and it is a little trickier but still easier from the bottom. One thing I have found on the passenger side is to unbolt the AC compressor and let it fall to the side. Then you can run your hand straight back and get the plugs pretty easily. The driver side will require the lower IC tube to be removed if you don't come up from the bottom. Hope this helps!
Ed Springer
90 Black XR7 5-speed: 70mm TB, Fresh Air Intake, Upgraded '94 Supercharger, 5% SC Pulley, Raised SC Top, I/C Fan, Underdrive Pulleys, Headers, Magnaflow Muffler (no cats) with stock resoantors, 3:27 Gears, Ripper Shifter, 73 CL MAF, Magnacore Wires.
94 Red SC Auto: 70mm TB, Fresh Air Intake, Stock 90 SC Pulley, Raised SC Top, I/C Fan, Underdrive Pulleys, Headers, Raven Muffler (no cats) with stock resoantors, 3:73 Gears, 73 CL MAF, Magnacore Wires, TRANSGO Shift Kit, Haydon Auxiliary Transmission Cooler.