Hello Sly;

I have the MX-170B in my C-172, and am using the same "V" nav antenna in the vertical fin.  What you will need is a separate glideslope receiver, and an indicator with the glideslope and localizer needles. The MX-170B will channel the glideslope signal but does not have the internal receiver like the KX-155.

For the indicator, a unit like the King KI-209, connected to a King KN-75 glideslope receiver will work.  I am using the King KI-214, which has the glideslope receiver built into the indicator and is a good option. However, the KI-214 is an older unit and repair parts are becoming scarce, so I keep a spare unit just in case the one fails. The Nav and glideslope antennas are connected through a splitter to the one nav "V" antenna in the vertical fin.

Your costs are going to be purchasing the indicator and glideslope receiver, the splitter, and the additional wiring that needs to be done by your avionics shop to make the Nav/Com connections.  Bennett Avionics sells the KI-214 for $995, the KI-209 for $995, and the KN-75 for $495. Often you can find these a lot cheaper on eBay, but will need to have the unit certified by an avionics shop before you install it in a certified airplane.

Of course there are other options, but the MX-170B is the slide-in replacement for the King KX-170B, and these are the most common units that were used with it. Using this option should minimize your installation costs.

Hope this information helps.

Jon