OP Here -

Thanks all. And yes, there was LOTS of crud!

To answer the question -

• RD is a Shimano XT CS-M771 and, as a temporary measure, I pulled a pulley off a Shimano Ultegra 6600 RD.

The worn pulley caused the new chain (Dura-Ace) to skip when I was dialing in the cable for the RD (done upside down). I took a 90-minute ride and it seemed reasonable. I replaced the crankset (new Ultegra 6603) and wheels (DT Swiss 4.0, takeoffs from a Specialized Roubaix Expert) at the same time.

Sadly my legs seemed just as dead as they had before I changed the drivetrain!