Typically, a dyno uses and MSD and coil it trusts, you just feed the trigger wire from your distributor, it'll ground at a 1/2 V or whatever the MSD uses and will be very gentle on points and dwell isn't an issue
If you do run your ignition completely, you likely have to step it down as you say. I would prefer the MSD option by a long shot, but if for some reason you need to, stepping it down through the coil is no different than stepping it down through the coil and resistor wire.