No mate, they are not that important to swap to alloy made item (even I changed all), as I knew you need 2 x "A" and 1 x "B" and 1x "C" (no "D"). IMO, the OEM plastic item already can stand for reasonable impact, but it is hard to predict the result if your car hasn't a bodyshell and foam bumper during the impact.
Don't know about optional shaft, never heard that and I expect it is show off parts.
By the way, it is nice pick for the M-chassis! I like mine very much!
thanks! yes there are no "D" for arm mount, if this is not necessary option then i can save some money, square bumper is already on it.
What motor and body shell you are using on it? can you take some pics of your ABC? planning to have 3000kv on this, but due to the space is limit, and most of the brushless
esc are "big" still not decide yet.