I need instructions of setting valve lash on 1965 273 2bbl

Notice in post #3, the instructions say to rotate every 90 degrees. This requires that the balancer be so marked either by a timing tape or by calibrating it.
Alternatively, you can pull out the plugs and find TDC of each successive cylinder in the firing order by Feeling it come up on a clean screwdriver. Do not stick anything in that hole that can break!,lol. You will have to pull the screwdriver out as the piston comes up, or it will jam.
Alternatively, you can stick a tight fitting hose just inside the plughole, and put the other end in between your teeth; then rotate the engine and feel the air coming into your mouth.When it stops blowing and sucks your tongue in, stop, back up, you are there.
Alternatively, you can watch the rocker arms on the cylinder that is exactly 1 turn further along in the firing order. When the two valves are just off their seats, the one opening and the other closing,bam, you are there.
Alternatively; posts 2 and 5 will get you there.

When sticking the feelers in there, use the very narrow kind. There may be grooves that have been worn in the rocker arms by the valve stems.The wide feelers will span across the groove and give a false reading.

Everybody says to set the valves on a fully warmed up engine. Good luck with that.
By the time you have pulled out all the plugs, removed the valve covers,etc, the engine is no longer warm. Then, from the time you start adjusting the first valve, until the time you have finished the last one, the engine will be well into it's cooling cycle. Go back and start over. If the first one or two cylinders are still where you set them ,then you are good to go.If they are not, check a few more.
On my slanty, it takes particularly long to get the cover off, and my balancer is marked. I still don't use the fully warmed up method.I determined a long time ago what the lash difference was from normal running temp to ambient temp in my garage,( about 65*F), and now do bi-annual checks at 65*. Sometimes every third year. Or on the 4th. Yeah I've had her a long,long,long, awful-long time; 23 years.