How far to rev this 273 commando build

For a drag race, that graph in post #6 tells you to shift just past the hp peak ~5500 - 5700 rpm and operate around peak hp.
It does no good to go too far past peak hp @5200 before shifting. You lose hp and risk hurting the engine. For top speed in 4th, the Commando engine goes easily to 6000 rpm.