Mike Richards - Specs for '56 and '55 are the same I think: this is book data...Caster: +1/2° to +1-1/2° - preferred +1°
Camber: +1/4° to +1-1/4° - preferred +3/4°
Toe In: 1/16" to 1/8"
Kingpin Axis: 7°-7'
I think the early Mustang spec's would be a better arrangement (for a start anyway)...
Caster: +2° to +2-3/4°
Camber: 0° to -1/2°
Toe In: 1/8"
pre-dates common use of radial tires
The lower control arms on our cars (birds 55-56-57) can - and have - been shifted ahead to gain Caster without excessive shimming.