Here you go:
http://www.jensonusa.com/!V7j9W8NQJ-L-cwFuKCpbOQ!/Surly-ECR-29-Fork?utm_source=FRGL&utm_medium=organic&pt_source=googleads&pt_medium=cpc&pt_campaign=shopping_us&pt_keyword=&gclid=CMjhpoHJ49QCFZSEswodAXYH3w
A couple of mm different offset will be unnoticeable.
Putting a slightly longer fork on will do the following: Slacken the head tube and seat tube angles slightly, raise the BB a bit. Whether those changes are positive or negative depends...
BTW, BB drop and BB height are different measurements, which one are you talking about?