The 273 used the same heads for the commandos and non commandos untill the commando went away in 68 then they used the 318 open chamber head. Absolutly nothing special about a head from a commando VS a head from a 2bl motor.

As for how many cubes they can support, well that depends on how many RPM you want to turn. The 273 D-dart engines would go 7000 so in a 360 that would equal about 5300 rpm. The 360 will unshroud the valves a little more so might go 5500, max ported with big valves they can mabey make 400hp on a 360.

For casting numbers they are probably a 315 or 920 depending on year. 920 was the 67 only head.