The STC that approves the MT composite hydraulic constant speed propeller has recently been amended to approve installation on all 170/172/15 series aircraft that are powered by ANY version of a Lycoming -360 series engine and any hydraulic governor. Two props are currently available. A 83" 2-blade and a 79" 3-blade version.
See the data sheets on the STC Holder website:
2-blade: http://flight-resource.com/Datasheets/C ... 2Blade.pdf
3-blade: http://flight-resource.com/Datasheets/C ... 3Blade.pdf
I had the luxury of trying both of these and the Hartzell Trailblazer on the same day on my plane to evaluate take-off, climb and cruise performance having previously tested the 83" 2-blade vs the 80" Hartzell Metal prop and the 76" Hartzell Metal prop. My plane is a 1955 C170B with a new O-360, Lycon polished cyl, lots of monitoring equipment and other mods.
I selected the MT 3-blade to keep for my plane. I loved the smoothness and quiet vibration free operation. It has the shortest take-off roll to lift off. The 2-blade MT was faster in cruise by about 5mph and a bit lighter, but I simply loved the way the 3-blade would operate at low RPM's and the sexy look! They are now building them with a stronger Nickel-Cobalt Leading edge that I have seen cut clean trough a steel tow bar with damage limited enough the owner was able to fly that pro home! Back in 2010 they changed the Kevlar wrap process to eliminate any chance of surface cracking in the epoxy/paint top coats and last year began using a new paint formulation that is really holding up well to use in hard rain. The 2-blde price is just under $14K. The 3-blade is about $2K more.
Best regards and Happy Flying!