[Accelo]

72c20customcamper;
I purchased a similar setup. It was a pain to get the lines connected.
I'm not positive but this master cylinder may sit further forward?
Inlinetube.com is a likely best source for the SS lines.
However, they are for factory parts.
I had to cut and double flair, one line, to get the stainless tubing to connect up.
The other had to be re-bent.
I had nothing by hassles getting my brakes functional and leak free.
It's kind of my pet peeve now.
Especially after my friend, with a 68 Camaro, purchased lines and they bolted right in.
He had hours into the project and I had days.

You need to know the lines are routed differently on the disc brake trucks.
The feed line, to the flexible line, terminates in the front of the cross-member.
The stock drum brakes feeds from the rear.
Two methods to deal with this;
1. Route the lines in the stock location for discs. Requires adding a tab to the front of the cross-member to retain the top of the flexible line. Also difficult to install with the motor installed as the lines cross over under the pan where there is little clearance.
2. Use the factory rear feed for the disc brakes. This means a custom rubber flex line. Some members were not all that thrilled with the hose routing.

Note: That dropped spindles can exacerbate the situation. The reposition the caliper in relation to the "A" arms. Be happy you don't have to deal with this extra complication.

Wilwood brakes costs more but it's an engineered package.
Others repurpose other parts and adapt them to the truck. Typically there is more install headaches on these systems.

To further complicate things GM also moved the rear attachment point on the rear differential brake line. It is on the side on the earlier trucks and was moved to the middle in 71.
So one can't just purchase lines for a 71-72 as you will need to change the front and rear line where they attache to the flexible rubber lines.

And I haven't even mentioned the K10 and the leaf spring trucks.
Yup, its stupid.
Cheers