Tony M - you are scaring me man!
The difference in 1/4 vs 3/16 tube sizes plays no role in distribution of pressure to the wheel cylinders at the fluid flow rates experienced in any normal braking system.
Using the 1" 1950 master cylinder will result in less brake pedal effort, but also less margin for acceptable brake shoe adjustment.
You will have to pay slightly more attention to how the shoes are adjusted - if you let them go for too long, you will bottom out the master cylinder before you reach maximum braking effort at the wheels.
So at present, you need the 3 rear axle brass blocks in size 1/4"?
