i currently have power drum and i'm converting to front disc. what i need to know is if i can leave the distribution block on and run the lines from the porportioning valve to it. with the headers on i cant get my hand in there to remove the lines so i figured i'll just re flare the lines at the master for the new valve. or should i remove the header and place the porportioning valve where the block is now. thanks

If you install a true proportioning valve you should remove the distribution block and replace it with the prop valve. If you want to leave the distribution block, you could do it like the factory did in 68 and just install the correct metering valve. The valve is installed under the master cylinder and plumbed into the front brake lines which run down to the distribution block.

if i understand correctly if i install a metering valve to the front line i dont need a porportioning vave. this way is quicker but will the brakes work good.if so is a metering valve a part that part stores carry or a specialty item

You will have to get one used, the correct piece was only used from 1967-69. A 1970 will also work but looks different than the earlier piece. The metering valve was gone for 71.