We installed the 270S in our 273. 2 barrel pistons. Too much cam for the heads and compression. Stock TC and 323 SG, LD4B.
I even did a mild port job, not near enough head for that cam.
Sounds great, lol. It will get the Commando pistons in near future hopefully.
Bewy will be along in a moment to tell you that you should have just kept adding valve lash until it purred like a kitten. That dodgy trick is so 1980's... lol.