It depends on what the person you were talking to had in mind when they said "plastic covering." All stock Isuzu Vehicross wheels have plastic centercaps, so maybe that's what the person was referring to?
If the person was talking about the protective coating on the aluminum of the wheels themselves, I don't think it was ever plastic. For protective coatings, most aluminum wheels generally have layers of paint with a layer of clearcoat, are powder-coated, or are chrome plated. The wheels Isuzu chose for the various years of VX were no exception as far as I can tell.
Most 16" wheels I've seen on 1999 VX's appeared to be painted silver with possibly a layer of clearcoat. Maybe someone with a '99 and stock 16"s can verify this?
And the stock 18" wheels on 2000 and 2001 VX's were chrome plated...albeit not very well.![]()