I just upgraded my 2017 iMac 27" with Samsung OEM MZ-JPV512S/0A1 it has nice speeds.
Those 1TB: Apple OEM 1TB MZ-KPV1T0S/0A1 installed in to the Mac Pro's i think it should fit same way.
Search for SSUBX one.
This one from Mac pro and fits like original also has metal heatsink plate.