Always try to run with vac advance if you can, depends what cam you are running, too wild and the pulses will be all over the place, as you are 2 cyls fed by one side of 40, vac signal should be ok.
If it has not been jetted to suit, then this is what needs doing, a rolling road is far better/quicker than trial and error, if you do run without vac I would put a spot weld onto plate to hold still, as vibration may move it.
tabetha