Black 1 inch JIS threaded headsets are available at http://www.alienbikes.com/gear.php with (I am assuming) a 32mm stack height as it comes on their frame which requires a 32mm stack height. Cost: $19.00
Also, find a way to measure (preferably with calipers) the diameter of the spot where the crown race is pressed on to (crown race seat).
JIS (Japanese Industrial Standard) bikes, which Centurions are due to their manufacturing in Japan, use crown race diameters of 27.0mm and ISO (International Organization for Standardization) bikes use 26.4mm crown races.
The Nashbar headset does not fit because it is probably the more common ISO standard.

Bam! Bumped to Senior Member Status