Alan, I don't know about your XC-70 but I HAVE to say this.

I set up to do the same thing with my V70 and "the shock mounts" were mentioned just as you learned.

The shock's top nut was on the shock's shaft which went through a hole in a larger plate of metal.
This plate was just that...a triangular plate of indestructible metal held onto the body of the car with 3 bolts. I didn't have to touch it.

WHAT MOUNT WERE THEY TALKING ABOUT?????????

Bottom bolt out. Top nut off. Down to the ground went the shock.

FCP allows returns on parts. I'd order by phone and mention this to the friendly rep.
Box your own returns for mailing (USPS) or shipment (FedEx, UPS etc.).
I prefer USPS for "regular sized" stuff.
Their "If it fits, it ships" flat rate boxes are quite expensive for many goods.

I had control arms to ship and their $20 box wouldn't accommodate even one. I boxed the pair myself and USPS postage was just $19.

Hope this helps.