[Frank-id]

Do not remove heads to replace valve seals. This is an easy task orcan be very involved.....
My recommendations are.......
only change the intake seals, use the ford type 5/16 inch umbrella seals, andget/buy tool for compressing valve springs while heads still on engine.An air compressor is required to change seals.
A tool that is required is an old spark plug. The spark plug must have the porceline, center electrode and ground removed. A short male quick air hose disconnect needs to be welded or brazed to the spark plug where center electrode was located.
Method of replacing seals is......
remove distributor cap to observe rotor position, remove both valve rocker covers,remove all spark plugs, and have method of turning engine over to each cylinder. The firing order for sbc is 18436572 and rotor will rotate clockwise as viewed over dist. Turn engine by some method till rotor is pointing at number one cylinder and verified by viewing timing mark on harmonic balancer and timing mark. The piston does not need to be exactly at top dead center to change seal. Next the tool for air connection is screwed into head , for the first one, do number one, front drivers side.
Connect air hose to fitting, which will pressure the cylinder and hold valves closed. Next remove rocker arm on intake valve. Use valve spring compression tool, made by KD #912, to compress valve spring and remove 2 valve keepers. Slowly relax pressure on spring tool and remove tool and spring. The oil seal can now be seen. Remove old seal and install umbrella seal over valve stem with a little grease. Reassemble the valve with the spring, retainer and 2 keepers.
The rocker can be assembled later after the other seals are changed.
The valves can be adjusted after all the valves parts have been reassembled.
Now is the time to adjust all the rockers. I usually release the rockers untill a loud clacking is heard and then rocker nuts are slowly tightened untill all noise is stopped and just 1/2 turn tighter.... I do this adjustment several times.