You might try asking bungle1 about this. (He's the one who made the head sculpture pack; bungle1 is his Rosity ID.) Unless the super model legs figure has a different head from standard V3, it should accept the morph.

Another possibility would be to check out the "frankensteining a head" tutorials at FallenCity.net. How to put one figure's head on another figure's body. It takes some work, but you'd only have to do it once.