Just did this last week myself. If you want to go down through the top your going to have to take off your coil packs. If you want to go up through the bottom your going to need a 3/8 swivel, and a few mix and match extensions. A swivel head ratchet helped a lot also. Either way (I tried both and finally succeeded through the top) is an absolute pain in the ass and will require patience, band-aids, and beer. Best of luck.
1999 Pontiac Trans AM. 6-speed. Performance: FAST 102 IM, NW TB, Hooker Super Comp LT's, Comp CAMS Top End, Improved Racing Pan Baffle, Full UMI suspension, Borla Cat-back. Cosmetics: Hurst Short Shift, Z-06 style wheels, with 1" spacers on the rears, Firebird emblem (painted).