There are actually two
roller coasters with this name, but oddly enough they have almost
nothing in common.
The steel version of GASM opened at Six Flags Great Adventure in 1989, on the boardwalk next to the Spaceship and the Parachute Drop.. Designed by Arrow Dynamics, its 3800-foot track is red with white supports. The coaster, which has seven inversions, reaches a height of 173 feet, and the first drop is 155 feet; its maximum speed is 68mph and the ride takes two minutes and twenty seconds. Three seven-car trains - one each in red, white, and blue - can carry 28 riders each for a total capacity of 1,680 riders per hour (who must each be at least 54 inches tall). The ride features Fast Lane, the Six Flags line-skipping service.
The other version of GASM is a single out-and-back wooden coaster at Six Flags Over Georgia. Designed by John Allen and built by the Philadelphia Toboggan Company, it opened in April 1973. The track is 3,450 feet in length and 105 feet high; the main drop is 89 feet at a 45-degree angle. This ride's top speed is 57mph, and the round trip takes two minutes; the two PTC trains allow an estimated hourly capacity of 1,200 riders.
Sources
http://www.rcdb.com/installationdetail34.htm
http://www.rcdb.com/installationdetail41.htm
http://www.gadv.com/screammachine.html
http://www.ultimaterollercoaster.com/coasters/yellowpages/coasters/greatamerican_sfog.shtml