I think you may be right. I just tried your truck, and went all over the place (10+ Repair Shops). I found nothing over 500hp engine. I don't know if this is a design flaw, or intentional. Sorry.

There must be an engine with more than 475 HP. For example the DDS575 or CP600.
The trucks don't have their own performance and security parts like chassis, engine, wheels, navigation and so on, they all are identical. Only the exterieur parts are special.
I remember driving around for a long time looking for classic wheels for the Western Star. After I visited a lot of service stations I found one that sold those rims. The same was with a windshield for the side window of another truck. Maybe it's the same thing with the engine of your truck.

Not in this case. I traveled to 7 more shops (17 in all). Almost the whole map. This could be the exception here.

Yeah i've looked all over from oxnart to Fresco and no luck...

Okay... then it really must be a bug that needs to be fixed. Together with the bug that only the Titan Alpine gets wet side windows and the Freightliner Classic never has rain on its windows when it's raining. But that's another topic...

Or it's as always in life. That you get such an engine in the very last service station. :-P

I don't think there is such engine for the Atlas :)
The highest HP engine i've found is DDS475 ...

Same here, but if it bugs you that much..... Just try a different truck. There's a bunch of them. ;)

The Atlas is the best looking truck in the game :P Atleast for me tho :)
Other one won't do :D

Well then you're just going to have to deal with the draw-backs. Personally, I think it has a slow accelaration, and a lower than usual top speed. Looking good just don't cut it for me if performance is poor.

yeah im with you I love the Atlas but IMHO the Phantom is the best looking but I looked and 475 is the top engine I can find for the Atlas