I just went thru this with my 71.
Though it was a GIANT pain in the ass to install the front lines. The main front to rear line should line up nicely with the stock location for the proportional valve. The clips that hold it on the firewall will not be real fun with the engine in place, nor the ones for the passenger side front brakes, but it IS doable. You will just have to remove the strut braces and the Blue emissions can to get access. Photograph each clip. some screws are longer than others so keep track of that as well. Note All of the connections were extremely difficult to get loose. I would suggest changing the original proportional valve and the hoses if you have not done so.
Much like Stanglover, I had to custom make the lines from the master to the proporotional valvle. They aren't bent correctly. I just went with some of the Nickle-copper lines from the parts store and used a tubing bender to bend them over. You should be able to find any adaptors you need at the parts store or some master cylinders come with the adaptors. Otherwise you will need to cut and flare the lines with the proper fitting. Very easy to do on the nickel-copper lines as they are nice and easy to flare with any tool.
I got stainless lines from NPD. If you have to make any changes to the line end fittings, well your going to have trouble without the proper flare tool. The typical flare tool will NOT work on stainless. Trust me, I tried. Don't even think about attempting it with a parts store tool. You will need a hydraulic tool or the expensive eastwood tool. That being said, I would double check that your Proportional valve fittings match the fittings in the kit your getting. That's the only place you will find any issues if at all.
2265-29S
BRAKE LINE FRONT TO REAR STAINLESS STEEL
2267-5S
BRAKE LINE SET REAR AXLE STAINLESS STEEL
2265-14S
BRAKE LINE SET FRONT DISC STAINLESS STEEL 5
This was one of the best upgrades I have done to this car. Since changing out the lines and replacing my leaking distribution valve, my brakes work 100% better.
If you want an easy flare tool to use I got this eastwood tool and it was great for the soft lines, but would not work on the stainless lines. It would flare the stainless but it would not seal properly.
https://www.eastwood.com/eastwood-on-car-flaring-tool-for-3-16-tubing.html?SRCCODE=PLA00010&msclkid=4d240a272cb11e2cc13f56839bedad1a