96 Riviera no spark

First of all, you should never change parts before you test them to make sure they're bad.

Next, do you have a "Check engine" light on the dash? If so, have the computer scanned first.

also, you didn't mention if you changed the coil packs? If not, test them. First find out if it's receiving voltage. If so, then when you crank the motor, is it getting a signal to fire. If the answer is yes to both, then the pack is bad. If the answer is no to one or both, then suspect the computer. (Only because there's nothing left to suspect, since you already changed everything)