American medium sized loco?

I have a ficticious route featuring US/Canadian rolling stock and was using my beloved (or content creators) Class 66 to haul them.
Having a change of heart I am using SD40-2s and the 44tonners for the lighter loads.
Braking is not too clever, is there a loco somewhere between, too much virtual diesel being used if all SD40s.

Edit: After googling what each manufacturer has built in the past I found a GE U18BL by davesnow fits the bill nicely, thanks Dave.

The equivalent of a U18B would be the EMD GP9 and SD9. These are still pretty common, despite their age, and are used on a lot of short lines and in switching operations. My local railroad uses the last three remaining units on light branch line operations as well as in the yards.

These come in a high-hood or short hood versions as well as with or without dynamic brakes. This is noticeable by the blisters on the sides of the body up along the top edge.

https://en.wikipedia.org/wiki/EMD_GP9

https://en.wikipedia.org/wiki/EMD_SD9

The GE U18B came out nearly 15 years later in 1973. There are many still in use today as switchers and branch line work. My local railroad scrapped theirs when they took over operations of a connecting line.

I'd second that.

You've got your EMD SD, 'Special Duty' 6 Axle Diesel, ranging from the 'high hood' SD-7/9, all the way up to the mighty SD90MAC.

You're GE 6 axles, C-44, AC4400, C-39, C40-8 and the like.

You're EMD 4 axles, classified as 'GP' locomotives. My personal favorite. There are many different versions, and many different schemes available to fit any era, any railroad. There are also smaller 'SW' switching locomotives, which are cool as well and also have 4 axles.

Then you have you're GE 4 axles, like that U18B, there is also the B class, such as the B-37.

All of these can be found in some form on the DLS thanks to Dave Snow, NorfolkSouthern37, and Sp0rbust.

Enjoy! Good luck in the search.