If your are wanting to switch to fixed blade broadheads you cann' t go wrong with NAP thunderheads. With light arrows you could use 85 or 100gr heads. As long as you make sure the head is tuned to the arrow ( spin test to make sure they are straight with arrow) they should fly fine. Have used similar set ups using light aluminum arrows and light heads at 75 lbs and 290 fps with no problems.
One other note the outfit you are using sounds fine with the mechanical heads.
Good luck
David/Mo