Where are the other four spark plugs for a 1992 Cadillac Seville?

A 1992 Cadillac Seville has a Northstar V8 engine. The Northstar engine didn't appear in Cadillacs until 1993. Therefore, a 1992 Seville would have a different engine, likely a 4.5L or 4.9L V8, which uses eight spark plugs, not four. They'd be arranged two per cylinder, one per cylinder head, in a typical V8 configuration. You'll need to consult a repair manual or a diagram specific to your *exact* 1992 Seville engine to determine their precise location.