The mirrors are , way over priced from the dealer, and high priced from salvage yards, because they are frequently needed for accident repairs. But a salvage yard price should be 1/2 of the new price, if you can find them.
The wiring and controls will be the same , if year is correct.
Edit: But you know that.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.