I have a close friend with a 1961 172 with a single Garmin 430W in it. It's not my choice of an IFR platform but frankly he gets more IFR time in it than I do. He does however have a vacuum pump (and for reasons I won't go into here, I'd not suggest ever planning an IFR flight with just venturis). Of course he is selective in the IFR he plans. His plane has other reasons it's not a tremendous IFR platform, the biggest is range. We both left the GSO area one time, me heading to CJR and him going up near Baltimore. I'm looking at my ground speed and note that I'm showing 90 knots against a 135 or so TAS. I figure he's having a lot of fun. He bails around Richmond and decides to drive.