Hello Nick,
you are doing a great job on this horrible base ... i know, what i am talking from - i try something similar - the re-invention of the kit. If possible i would like to contakt you via e-mail an share some things, like etched parts for the dumpers i have almost createtd ... may be, it will help you. Wheels i did already quite similar to yours and the engine has been tuned by scratching - your engine ist just great, congratulations!
Hope to get in contact with you - Kai