Chosen Solution

15" MacBookPro Core Duo - A1150. Do you know if the WD 1TB drive will fit? It’s 12.5mm thick rather than 9.5mm, and I don’t want to find out the hard way

Take the drive out. It’s just the three screws in the ram bracket and put some old playing cards on it till you get to the correct height and tape them down and see if it will slide in.