Rear wheel cylinder help

They both could be correct,, depending on application,

I would hazard a guess that 1 3/16 would prob be best on a manual brake app.. and the 15/16 for power.

The Master cyl bore would also have some bearing on which to choose..

JMO...

Isn't it recommended to use a smaller bore MC on manual brakes?

That's the only reason I was thinking the way I was.