I have all the parts to do the Scarebird conversion on my 6cyl. I am going to keep it 4-lug so I can use the wheels I already have made. The instructions say if you are using a disc-drum MC you do not need the to install the adjustable proportioning valve. I purchased a 67 disc brake MC for my swap but I still question the need for the proportioning valve. Can I keep the 6 cyl drum brake distrubition block and add a adjustable proportioining valve on the rear line outside of the block or should I just buy the 67 disc brake distribution block and be done with it?