I aquired and entire disk brake setup from a 71 Chevelle. Using a 74 vette non power master from SSBC. Lines were NG in the 71. Has anyone had experience using the existing lines (Front drum). Is there a recommended kit if larger ones are needed? Also looking for input on the P valve..

You can use stock brake lines, it doesn't matter if your brake system is disc or drum on front. The hardest part of an conversion I've done is locating the combination (aka proportioning) valve. I didn't like the looks of it hanging onto the master cylinder, so I put it where the junction block is bolted to the frame rail. I effectively replace the junction block with the combi valve. But many conversion kits, or some later model chevies have the combination valve bolted to a braket that is mounted on the master cylinder. This works good too, because the new lines you need to make are right there in front of you. Go to the master power brakes website, I believe it's mpbrakes.com. They used to have a great explanation for all this stuff and their prices on combi valves, etc are reasonable.

Chuck the old lines, if they are orig. they are junk! Brake fluid attracts moisture (water) that sits in the lines for 40yrs!!! We have complete prebent hardline kits....Much cleaner and easier!