I would second the Cannon Fodder suggestion, with some Stargrave/Frostgrave/Oathmark heads (and Stargrave arms) for commonality/variation.
Stargrave head and WA weapons sprue arms.
Oathmark head and Stargrave arms (some filling required at the back, Stargrave figures are much better fed).
Great Escape Gunfighters might also be a source for arms (and heads).