The 3racing gear diff is the best for this chassis. Just check the left right play after the first runs and shim if necessary. Also don’t use the bevel gear that comes with the diff!
The Yeah racing motor mount works fine.
Everything else would I buy from Tamiya, because the quality of Yeah- and 3Racing aluminium parts is questionable...
For the suspension go for Tamiya graphite arms and hubs. They will stiffen up the suspension and make the car a lot better. If possible not the 416 arms, because they will make the car even narrower. If your wallet allows it go for dcj in front.