Both Year One and Megaparts get their wiring harnesses from M&H, the backorder situation is with the supplier not the retailer. Worth checking though, to see if they might by chance have a set gathering dust in their inventory.
Anyone know how long M&H is backordered on harnesses these days? I ordered a Challenger rear harness from Year One before xmas and haven't heard any updates from them after I ordered it and they said it was backordered. At least they had a front harness in stock they sent me! I hope I get my rear harness by late April but I'm starting to get worried.