I'm pretty sure the actual size of the pickup from one end of the bobbin to the other (low E to high E) is the same between the two. So like the others said, it's just the spacing between the poles. 53mm (F-spaced) will line up under the strings a little better on most Floyd-equipped guitars. I've used both sizes on 'Fender'/Floyd guitars and never noticed any appreciable tonal differences between them. You might have more of an issue with the depth of the pickup. Not sure if the Peavey and Suhr pickups are the same. Hopefully it'll be an easy swap.
I hope you dig the Aldrich too. I have them in a Suhr Standard and LP Custom and they kill!