Sounds more like fuel starvation, are the float height correct, could always up fuel height a touch, or check the fuel pressure, what carb/s are they.
Could be the coil but they usually just stop when hot or misfire permanently until cooled a bit.
A lecktronic dizzy etc could be used, if different cam/and or carbs are used the igntion curve is highly likely to be a million miles out for best running.
Usually needs a lot more intial advance but less total, this can be achieved by bending the stops, get it running perfect low down, check to see timing figure is, then progressively bend tab in to limit total advance, if too much advance would likely cause a bit of damage long term, failing that it's a dizzy swing on a dyno equipped with dizzy plotter etc.
tabetha