I used the 6203-2RS and 6005-2RS. Fordem gave the idler, so the other must be the tensioner. Granted my swap was for a J18. I haven't eeded to swap them, after doing the J23 swap.
I bought new pulleys with bearings and kept the used pulleys. I took the used ones and installed new bearings to keep on the parts shelf. That allows me to have a spare set with new bearings ready for install. We were doing a lot of coastal runs with salt water. I was going through bearnings every year or so.