my 2 cents on original question.
In 1992 heads started coming from factory with the snap rings on the exhaust guides. '91 and previous had a TSB that describes cutting tool and snap ring installation. If heads have ever been redone, they will most likely have the snap rings on the aftermarket exhaust guides.
The Steath/Diamante had different cams. Some cams have marks on them,, but the marks change location with each production run on these so I wouldn't trust ANY markings.

dave h.
'89 Raider V6 5spd;Aisin Hubs;; Gen2 LS: frt. brakes, rear coils;U.C.arms;R.trailing arms;idler arm; rear LSD axle w.disc brakes ;2 battery system for Dog's fan; relocated ECU; custom bumpers;J.Baker receiver;Conferr roofrack; t-bar crank.