Which ballast resistor to use depends upon which distributor, coil, and ignition box you are running..

The primary purpose of the ballast resistor is to limit current not voltage to the coil..
Certain later aftermarket coils can take significantly, higher current (and voltage) that the earlier coils.. As well as certain boxes may be triggered by an analog or a digital signal which directly affects the amount of frequency/time the coil is being fired..

Disclose what distributor, ignition box and coil you are running then we can post more specific relevant comments..

Just my $0.02...