Transmission leak at shift leakage. How easy of fix and parts needed.

With that old cork gasket, it's likely to cause more leaks than cure if you cinch it down much. "Shift Shaft Seal" (say that 3 times fast!) Or you could call it a selector shaft seal. You'll probably have to pull the trans pan and drop the valve body so you can get the selector lever out of your way. I say probably because it's been a very long time since I've been under a '70 and because that's how most Ford transmissions are set up. Don't forget the dipstick tube. They can leak too. It's very possible that you wheel cylinders are leaking but a quick check: remove the vacuum check valve from the booster and stick a piece of light wire to the bottom of the inside of the booster to see if your master cylinder could be leaking into the booster. If it's a wheel cylinder, flush the brake system. replace them both and replace the brake shoes - the whole set. Don't try to shortcut your brakes and you won't regret it - or worry about it either.