Modern avionics puts a lot of information in a very small space. As an example, the Dynon D180 puts all flight instruments and engine instruments in a package 7" wide by 5" high. Couple this to a Garmin SL30 at 1.3" high and you've got NAV/COM/LOC and GS that displays on the D180's HSI. Add a GPS/COM such as any of the Garmins and that can couple to the D180 as well. Add the autopilot servos and you're away to the races.
Dynon is only one example of the many EFIS that are available today. Blue Mountain, Grand Rapids, MGL, Chelton, Avidyne, and Garmin are just a few more.
http://www.rivetbangers.com/BuilderResources.shtml is a fairly good list of manufacturers.
NeilK
2007 Long-EZ C-GNEZ
0-320, Dynon D10a, TruTrac
and other toys.