There was also a round 'gauge' cluster that only had the fuel gauge. The oil/temp/volts gauge locations just had dummy lights like the wide sweep cluster. Some had a clock in the tach location, some had a tach, some had both if I remember right.
Also, the round gauge setups with just dummy lights instead of actual gauges weren't plug & play compatible with the center 4-gauge group, the actual cluster housing is different.