74 custer is the same the earliers, just the face changed due the icons. If you fit a 73 Bezel on a "74" cluster will get a 73 without diff with original 73s

then also on 73s Speedo changed to 120 miles and blue/horizontal high beams pilot light.

But those stuff are parts of the cluster, not the cluster itself.

The DOOR LOCKS signal on the picture... I think those were sedans, not 2 doors, but not sure about though. As far I know you could get also JUST the seatbelt light too. At least locally they got ( not everyone ).

Tach harness is an ADD ON harness to the underdash harness. You don't need to modify anything to fit a tach harness to the underdash harness, just locate the terminals and plugs on the right locations. Same about clock where unique wire required is a small black wire hooked to the amm stud.

You can modify a non clock/tach housing cluster to fit a clock/tach. Locations are on casting, but requires job to modify, and get teh complete meters setup