Last set for a MK 1 touring car the rear bumpers were stock as rear arch wraps to it. All you would have to fabricate is box along doors or modify
Unique rare item, looking to get them reproduced but clearly more offsets the mould costs.
Before you ask I have not got a price yet, as few places I have phoned seem (well to me) want silly money to set up molds circa £400 mumper and £200 wings.
So they may end up in the loft once more.