I still have the Epcos, in case you want to ignore my critique and make me an offer!
I broke that rotting muffler syndrome by acquiring a stainless steel exhaust system from Breakwell&Green, an English firm that used to advertise in Roland's old Vintage BMW Bulletin, the fit and finish were great, (you can [almost] see both bike/exhaust as they are today, 40 some years later, in the photo to the right>) and these old systems still show up at swap meets from time to time.
If your bike must live in a damp environment, SS will prove to be economic investment.
Don is correct; being stainless they turn a lovely straw color, rather than the blue that chrome does, when subjected to the high temps.
And I agree with Kurt; one may not notice a lack of a cross-over pipe, but they are there for a reason, to balance back pressure between the cylinders; BMW would never have spent the money if not deemed necessary.
Not noticing a difference with or without the cross-over is probably akin to not noticing a lack of neutral steering if using different sized tires front and rear, which many of us also fail to note, so no harm no foul.
And finally, agree with James; put those nos mufflers on the forum For Sale section, along with your current mufflers; they look like maybe the ones Bill Swirin used to make/sell, and there's still a small market for pipes that are a bit louder than stock; the returns might go a long way towards your new pipes.