Found these local for a good price a while back. Just had time today to see if they'd fit. Don't mind the white paint on the top. For some reason the wrecker who dismantled the 135i figured he'd spray some paint on them to distinguish left and right.
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Though not a direct bolt up, with custom or different brackets they will work.
In this picture the caliper is only bolted to 1 of the mounting holes on the knuckle. The holes on the caliper bracket are slightly closer together on the 135 compared to the E60 caliper. With the caliper centered on the rotor, the bracket is spaced roughly 10mm away from the knuckle. Also the calipers being made to fit a 26mm thick rotor, they do fit the 30mm E60 rotor. As you can see in the next picture though for piece of mind I will probably have the inside of the caliper machined depending on which rotor I decide to run. The area between those 2 point just above the pads is just a hair over 30mm. Lots of clearance other wise.
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Next I'm going to try to source some brembo caliper brackets made for the M5 and see how they fit up.
Also those little blocks on the top and bottom of the caliper are just bolted on and can be removed. Not 100% sure what they're for, but from what I've read they are some sort of dampeners. Not very aesthetically pleasing though.

 

Where you bought those ramps to lift the car?

These calipers looks nice!

 

Looks interesting. Any reason why you didn't go with the M5 brakes? Was it just for the look of the caliper or was it a lower price.

 

Just from a local aftermarket parts shop.

As for the calipers, the price was great, they look at lot better than the m5 brakes, the surface area of the pad is very big, 6 piston,

 

do you get better braking?

whats needed for this conversion?

 

These calipers definitely look better than the M5 brakes however the trade-off is that you are still using your factory rotor size while the M5 brake setup is more of a BBK with larger rotors. I'd be interested to see the results once you have them all fitted.

Can you confirm the 135i pad width is the same as the stock pads? Looks like the pad wouldn't cover the full width of the rotor...

 

I plan to use larger rotors. Probably m5 or m3 rotors. Theres a m3 in the shop at work. I'm going to take some rotor measurements off of it. In the picture you can see the pad sits a little bit away from the top hat but it over hangs the edge of the rotor a little bit. With the m5 rotors the pad might not cover the whole surface of the rotor. Once I gather some more parts I'll post some more info.

 

So I measured the M3 rotors and they look like they're going to work. The difference is roughly 5/8ths from the front of the top hat to rear of the rotor. (M3 being shorter) Every other measurement, including rotor surface thickness, is the same. Except that the M3 rotor is 360mm diameter compared to 545 348mm.
I'm choosing the M3 rotors over the M5 rotors because the M3 is 30mm thick and the M5 is 36mm thick which is probably too big for the calipers.
So next I'll try to source some M3 front rotors and I guess I'll be making some custom brackets.

On another note; I changed my oil today. Switched over to Liqui Moly. After removing the oil filter I came to the conclusion I'll never use a fram oil filter again. It literally fell apart in my hands. It was replaced with a mann filter and I also installed a magnetic drain plug.