Timing belt and water pump, get the LS for both. What seals are you looking at? If you're looking at seals that go in the head, you'd need them for the SI (assuming it's a b16 head). For headgasket, you'll need a modified OEM headgasket...check out
www.goldeneaglemfg.com for good headgaskets.
As for the OEM parts, check out
www.acuraautomotiveparts.org for the pump and belt.
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2015 Ford Mustang GT Fastback - Ingot Silver - 6M - Performance Package - Gibson Catback, JLT CAI, FR 47lb injectors, BAMA E85 tune, Eibach Sportline, BMR wheel hop kit, UPR oil separator, Steeda shifter bushing/bracket
Team B.O.B.® - Ballaz on a Budget