How long are the nacelle strakes on a GE-90?
You can measure this on photos. 


Find a nice side view that shows the nacelle strake. 
Measure the engine diameter on the photo. 
Find the engine diameter in the engine specifications.
Calculate the ratio between the two. This gives you a scale factor of the photo.
Measure the strake, multiply by the scale factor to give the size of the strake on the real engine. 
Divide by the scale factor of your model to get the size of the strake on your model.


I use a spreadsheet so I can do step 2-6 once. I then create a formula that converts a dimension I measured on the photo to the one I need on the model. Makes it easy to do lots of measurements on a photo.
I usually import the photo into an application that uses SI measurement units (Adobe Illustrator), but you can measure in pixels too (which allows you to use cheap image tools).