Depending on what you have available for tools will depend on the amount of work you must accomplish.
If you have an air compressor then you should be able to accomplish the whole job in an afternoon.
Remove the rocker arm covers, remove the rocker arms,(count the threads as you remove the rocker arm nut) as you work on each cylinder, remove the spark plugs, make a short length of airhose about 20 inches long with a 1/4" male NPT adapter on one end and the quick connect for your air hose on the other. Screw the airhose adapter into the plug hole of the cylinder you are working on, this pressurizes the cylinder and holds the valves up. Use a special tool either from an auto parts store or a home made tool to compress the valve springs, remove the keepers, remove the old seal, make sure the seal groove is clean, install the new seal, keeper, release the tension on the spring. Make certain the keeper is seated, do the other valve seal in the same manner for that cylinder. When both are completed, release the air, re-install the rocker arms and tighten down the same number of threads you counted when removing the nut. Go on to the rest of the cylinders the same way until all are completed. Set one rocker arm cover on loosely to contain some of the oil, start the engine, adjust the rocker arms as you normally would, then do the other bank. Replace the rocker arm covers, using new gaskets. Clean up the mess, top off the oil, or change it, and your finished.
If you find that you have worn valve guides, where the valve can rock back and forth, then you won't solve your problem with just seals. The newer heads and valves are much better than the early SB valve head combination. The early valves had very small concentric grooves around the valve stems to help control the oil by the valve guides, this acted like a miniature hack saw and wore the valve guides out very rapidly. The newer valves are now smooth, and the valve guides have the concentric grooves to help control the oil, thereby causing less wear.
vettepilot