Would be interesting to see how long these parts last. I rather sacrifice weight for durability.

The stock front suspension block is G/G.

What will running F/E or E/E do?

going to e/e will narrow your track width which will increase your traction in front and make your steering more responsive. By using the f block in front with the e block in fr your track width will be the same as with the e/e but you will also add a half degree of front arm sweep. This will decrease entry steering and increase rotation through the middle and exit of a turn.

Thanks!

It will improve your turning on less grippy tracks. You typically want wider track length for higher grip tracks.

What would the parts be worth from my 419x which has been upgraded to an XR?

I was thinking of sticking it on eBay, there's the top and bottom deck and also the bulkheads , motor mount, servo mount.

must be worth something to somebody?

。。。sir , i can build a car out of those....if i can find other bits on the motor mount : )

Lol. Well I've stuck it on eBay should anybody be interested!

UK shipping only though I'm afraid

https://m.ebay.co.uk/itm/Tamiya-trf419x-spares-bulkheads-top-deck-bottom-deck-/283047053022

New TRF parts announced
 

TRF 419 - full aluminium diff housing - Tamiya #42325

https://cimg8.ibsrv.net/gimg/www.rct...4d099ae22b.jpg
Also good for TA07Pro/R.
Source: Facebook - Mokei Kagaku

So we would also need to buy the other side: Tamiya 42310 37T Differential Pulley, correct?

Yes, thats correct.

what is the point of metal diff housing? no crack, lighter, or else.

Been using that 42310 since day 1 with my TRF419x. I am yet to try & compare how the stock/plastic pulley is.