You will need extra shims (3mm) for the shocks - 1 under each piston - and some extra 5mm for the front hubs. They are better with locking metal hexes, but still not perfect.
Metal gears for the diff I wouldn't bother from the get go. When the plastic wear out, yep for it. Sand them down to 3.60mm and 4.55mm.
The alloy bulkhead parts do look nice, however, They are heavier though. And..... by the time you buy them you should have just bought a 418! I wouldn't, but I've got a 418 myself, so less inclined
Shim part numbers are 53585, 86 & 87 (3,4 & 5mm)