I can tell you really that the bumper on the DE edition is no longer available.

I tried to buy it last month from Wolf and the item had cancelled from my order because according to Wolf there is no definite ETA on it being available back in stock. Hence no back order.

The red alum. upper bulkheads are either available in limited quantities by request or are no longer available any more. Either way, their pricey at $55/ea.

Not to worry because those parts were basically bullet proof. You will never have to replace them. It just sucks for guys like me trying to mod our existing E4s to get that durability.