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Since I have done some research on the matter, and found that there is not much information on the belt routing and belt size for an A/C delete, so I decided to share what I learned after surrending a few hours at the local auto parts store figuring this out. The E90 N54 A/C bypass belt thread that inspired this one can be found here:

https://www.reddit.com/r/E90/comments/ecptq6/e92_335i_n54_serpentine_belt_replacement/?utm_source=amp&utm_medium=&utm_content=post_body

Background: I have been hearing some strange noise coming from the driver side of the engine bay. I figured it was the A/C based on the kind of noise it was making. I decided to go to the store today, and upon starting the car after coming from the store, the noise intensified and got some screeching coming from the engine bay. By the time I turned of the car and checked the engine bay, the A/C clutch was destroyed, resting on the ground, and the broken pulley was just sitting there, on the compressor shaft.

I did see me research trying to find a belt that would fit the E60 N54 while bypassing the A/C compressor. I found a thread that suggested a 7PK1440, a 7 ribs, 1440mm (56.7 in. aprox) Belt with a diagram suggesting the proper routing the the E90. The problem I faced is that on the E60, the A/C return line runs very close to the engine block, and interferes with the belt if you run the belt straight from the crankshaft pulley to the power steering pump, like it is suggested in this picture:


Suggested belt routing for N54 for the E90 platform. Taken from the Reddit link posted above

This led me to believe that the variety of routing options for the N54 depends on the platform, and that the E60 belt routing is not exactly the same as the E90 routing. Here is what I think the original routing for the E60 looks like:


This is the way the belt was routed in my E60 N54, and it seems to be the same routing used in the 135i N54 (https://www.1addicts.com/forums/showthread.php?t=1063860)

Now, to the core of the matter. Since this might be an emergency fix, I will give you a range of sizes for the belt to use on the E60 N54 to increase the odds of you finding a belt at your local parts store.

The smallest belt I would use is a 4070648 (Continental part number), which has 7 ribs, and is 64.8 inches (1646 mm aprox.) long. The longest one I would use is the 4070658 (Continental), which is also 7 ribs, but 65.8 inches (1671 mm aprox.) long. In other words, any 7 ribbed belt between 64.8 and 65.8 inches would probably work. I think the best fit is probably the 4070654/4070655.

And here's how I routed the belt:


I hope this information is useful to you, guys!