Front to rear brake line size?

So I'm going to be putting new brake lines on my '68 notch, and the only line I didn't buy as a preformed stainless line from classic industries was the line that runs from the front distribution block to the flex hose at the rear axle. I didn't buy it for budget reasons, and I figured that it would be relatively easy to replicate out of Nickel-Copper line until I get the proper stainless one ordered. I'm curious if anyone knows what size the line needs to be and which fittings I need to buy? The car is currently parked in snow so I'm not that enthusiastic about crawling under it to look until it's inside the garage. The car itself is a '68 Notch, originally a 318 2 barrel with a 7.25" rear axle, but the previous owner put an 8 3/4" axle in the car.