Just did my front disk breake conversion but I'm at a bump in the road. MY 67 was drum/drum and had a prop/switch valve mounted to the frame. As the kit plases the disk/drum prop valve up high by the breake booster, my break lines now stop at the frame and are 10 -12" short. Is there a way to couple the lines? Use a "T" block to feed the front breaks? Has anyone run into this during there conversion?

I'm in the middle of the same thing--I haven't decided which way to go yet. I didn't really want to run a new line to the rear. If I find an simple solution first, I'll let you know.
I wanted to leave the prop valve down low, but then I kinda like it tucked up at the master on a bracket. My old one was just floating over the frame rail (Someone had welded a clutch cross shaft bracket in that area)

in 67 the block on the frame was just a distribution block- so just remove it- and run short lines from the new propvalve & mc down to the old lines and use flared seat couplers to connect them.

I just did the four wheel manual single pot master to front disk manual conversion on my 66 using the Ground Up kit. I also bought a complete set of repro brake lines for the kit

Since I did not use the booster, the three lines that come to the prop valve were a bit too long. It was easy to just cut, rebend and reflare them to fit to the prop valve.

Or, you can just bend up a new line from the valve, and then put a flare union down by the frame somewhere.