small hole is MK1 Cortina and Anglia, the slaves come in 2 bore sizes, the larger bore size is for the twin cam ( elan and Cortina) use a jubilee clip as well as the circlip to hold it in.
throw the larger holed iron one away, its from a MK2 Cortina and you won't get the bits without getting your leg lifter right royally, and they're a bit crap anyway.
next thing is look at the bellhousing . . . the ally one ( and an iron twin cam one) is larger and radiused as the twin cam runs (or should/did) an 8 1/4") clutch. the standard Anglia and Cortina comes away from the flange/block at 45 degrees in a straight line, its for a smaller 7 1/4" or 7 1/2" clutch
If you fit a big clutch with a small bell housing you'll need one hell of a starter motor, I've taken a few calls from people building 'kit cars' saying their engines seized in the past . . . .
worse still an engine came back for a rebuild with chunks of dynamically balanced clutch cover sliced off with an angle grinder!!!
use all the mechanism and twiddly bits from a MK1/Anglia . . .it all works perfectly well if its in good nick.