[Tom Goldman]

1" Might be a little small . It might work if the pedal ratio is low ,like 4-5 to1.like many power units use.
Robbie , I suspect your car was also manual brakes ,so the ratio is probably at least 6-7 to1.
Since you will be using 4 piston calipers ,I'd use at least a 1 1/16", or even a 1 3/32" bore cylinder.
You should be able to stop with normal pedal pressure. ...The smaller bore will give higher pressure with less effort, but it also makes it easier to lock the brakes when stabbing the pedal .