IIRC, it is indeed 4" speakers that go in the front stock locations. I'm in the process of tearing down my door panels to add 6 1/2" units instead by adding pods and fiberglassing the panel. Though the screw 2 screw measurements are longer, the speakers you are looking for will be listed as 4's.

3.2L V6 SOHC 1996 Isuzu Rodeo. Flowmaster exhaust / K&N High Flow Intake / Kenwood headunit / Audiobahn Subs / Alphasonik/Kenwood/Sony Amps / 180 amp High-output alternator / Redtop Optima battery / Custom hood w/ scoop