The two vehicles you’ve mentioned are, in fact, fundamentally the same vehicle. The only difference in the rear bumpers of each was that the base-model Prado’s bumper was finished in grey plastic, while the upmarket Grande’s was body-coloured for a more integrated look. So, yes, the two bumpers should be physically interchangeable. The only difference in any of the Prado’s side mouldings was that the entry-level model, the RV, with its skinnier wheels and tyres, didn’t have the wheel-arch flares, so the moulding that joins the rear bumper to the rear part of the wheel arch would be different on the RV compared with the other Prado trim levels.