Honestly, the grey on the engine should be chromed, i don't have any chrome parts. However, i tried painting those grey pieces with metallic silver model paint, brush marks annoyed me a lot, so i left it as it is. Additionally the exhaust pipes on the fake engine could be chromed too, again the same method of painting them didn't work.
I also ended up having not enough black tiles to cover the top of the battery box :) it also already got quite heavy for one XL motor to drive it, lost quite a bit speed with how it currently is.
I totally agree with the grill. Red 2x1 grill pieces covering the bottom half of the grill might have looked more blended in, yet i don't have red grill pieces :)
I worked on this for almost about 2 months on and off. I got to the point of abandoning it a few times, so i didn't order and wait for any specific parts. I just found myself wanting to complete it as it is.
Thanks for your support and constructive feed back everyone.