I have a 70 Chevelle with manual brakes and drum in the front. I am going to put power disk brakes on the car. I have seen a little block mounted on the booster and am not sure what its for. Do I still need to change the proportioning valve or do I need to find this block thing on the booster?

Im pretty sure that is the proportioning valve. I found one for my swap and everything works great. Mine is on a 68 chevelle