stay with the 4.6L for pure bragging rights, Ohh what my little old 4.6L beat your 6.2L? awe whaaaa, But yeah anyways. Stay with the 4.6L its cheaper and the saleen unit can bring you to 600hp with some long tubes and forged short block of course. maybe some blow cams, that thing will turn out nice!!!
GL with your adventure ahead! Your choice, do some research dont take anyone elses word

its all opinion to a certain extent.
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My Car - 2007 Alloy GT Mustang Coupe Automatic.
Steeda CAI, UDP//
SCT Xcal II //
Magnaflow 2.5" duel Cat-back//
Pypes Off Road H-pipe//
FRPP 4.10 Gears.
Shelby 14" Break kit//
Vogtland Springs //
J&M Billet LCA, UCA, double adj Panhard Bar, Camber Plate.