Marine 273 build
That is one nice 'wave rider'.
The 273/235 HP Commando is really closer to 215 HP {true NHRA racing numbers}.
The 340 Camshaft will probably add {+15 HP}.
And the Intake and Holley {600 CFM} Carburetor will probably add another
solid {+15 HP}, especially above 3000 RPM's.
The Cylinder Heads, more of 'any little porting helps over no porting'.
Generally, even a 'general smoothing job', and matching the ports {gasket port match}
is worth an easy {+10 HP}.