The ESP Guitar Company

try searching using google and identify the model of the pickups. 

I have, but so far uncle google has failed me. It bugs me that this information is so hard to find, that's why I have come here in search of an answer. I also know that f-space is very widely used for guitars with trems. However, I still don't know if this is an definite truth for all trem guitars or floyds or whatever.

Yes, it's F-spaced.

Thank you Pushead, just the answer I was looking for!

Actually, I just got an e-mail from ESP support (better laaaate then never):

• Hello,
  The pickup installed on the LTD/Alexi-200, LH-301B, is standard spaced.
  Best Regards,
  
  Customer Service

So, yeah. Confused now, but I guess I'll just measure it myself eventually.

EDIT: I received another e-mail that clarifies everything:

• Hello,
  As a follow up to our previous email, we realize our response may have been too vague.Clarification about the construction of the pickup should have been provided. The LH-301B uses bar magnets that allow it to cover the range needed for guitars that are equipped with either the standard TOM spacing or equipped with a Vintage/Double Locking Tremolo. Essentially it covers both Standard and F-spaced ranges all at once. 
  All the Best,
  
  Customer Service
  ESP Guitars

You'll need an F-spaced replacement for it.

In my experience if your dropping another high output pup into your guitar it shouldn't matter to much. It shouldn't have to much of a tonal effect on your guitar other than the voicing properties of the pup. Have fun with it.

Rule of thumb: If the guitar has a Floyd Rose or any other sort of Trem it's F-spaced 99.9% of the time. If it has a TOM, its not F-spaced. However, if the magnets/pole pieces use bar magnets, like say the DiMarzio X2N, then string spacing doesn't matter because the the strings will still be over the top of the magnet regardless of string spacing.