I have a 2003 F-150 STX w/ 4.6L RWD and I'm having trouble with a cheap alternator the previous owner installed on my truck and was wondering if the higher amperage 5.4 alt. will bolt up directly to the 4.6 block. Or should I shell out the extra cash for a "higher performance" one instead.

 

not sure about the high output alternators but i know the 130 amp alternator off a 5.4 will bolt on a 4.6

 

You want the large case 130 amp replacement. The case with two holes (see where I circled) in the ribbing is what you want.

 

Please note.... those alternators above are for a different motor (I believe the 4.0), but the same holes apply to each.

 

What white said. ^^
And there's no reason to go with anything bigger than a 130A alternator unless you have some hellacious lighting or other monster loads. (Although I *did* install a higher-output coil when I rebuilt mine, because it wasn't much more expensive.)