Hey purpletimbo can you verify if the bearings in the car are metric or imperial? I've been told it's metric but i'd be really surprised if they went to the effort of remaking the moulds.
Those duratrax wheels may be the right offset but they're only 1.25 inch wide. B3 widebody rims are 1.5 inch wide same as B4.
I wanted to swap rims between my B4 and B3 so I made these longer axles with spacers..
But if you look at the B4 the rear arms pivot from the same distance out from the centre and are the same length, the way they changed the offset on the B4 was to offset the
hub carrier further out. So you could probably use B4 hub carriers (with the hinge pin hole drilled to 1/8") and driveshafts I haven't tried but will, waiting on an order from tower to arrive with some extra hub carriers. I guess it would end up slightly narrower on an RC10 though because the hub carrier isn't offset quite as far in as the B3 one.