For 91 there were two basic versions of the 5.0 motor. The HO 225 hp in Mustangs, and Linclon LSC's This has the SEFI system with the HO firing order cam and different heads compared to the non HO motors. The Thunderbird/Cougars had a unique intake manifold and 200 hp, not sure if those were SEFI, or what heads or cam they used.
The standard 5.0 was 150 hp found in Crown vic's etc has a batch fire injection and a traditional 302 firing order, and the crappy heads. Most apps also had the intake plenum pointing to the drivers side as well. Hope this helps.
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Frank W
90 5.0 LX coupe Daily driver. Silencer removed, K&N filter. Flexalite fan, 3 core radiator. FMS flywheel and Clutch, FMS blue wires Energy Suspension end links
88 Notch 2.3L 5 speed Parts/beater car
My two Notchbacks
74 Chevy Laguna Type S-3 305 Finally fixed getting a 454 to put in garage
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