Kurt Ullman wrote:
Is there anyway to use existing vents for attic fans or is taking a
big chunk out of the roof the only real option?

I did. I used a thermostatically controlled fan mounted in the north
gable vent. I profiled the vent, cut a triangle out of 3/4 plywood and
mounted the exhaust fan in that. My logic was; the south wind is
dominant so working with it seemed the proper thing to do, in the
winter the wind becomes northerly so having the vent partially blocked
again seemed prudent. I seems to work well, though it runs more than
I'd prefer. I also have a south gable vent an east facing dormer vent,
and ridge vent but no soffit vents as the design is open joist rather
than soffit and facial. I plan on converting it to soffit and fascia,
at which time I will drill the covers between the rafters and install
some sort of soffit vents