I bought a C150/150TD in 2008, new paint, 10 SMOH, $36K. 1964 model, original gross weight 1500, bumped to 1760 with the "texas" engine upgrade. Weighs about 1240 right now with 850's, minimal panel, and no vacuum system, so not a helluva lot of useful load (520#). $50K for the linked airplane seems a bit steep, esp in this economy. Esp with 1200 hours on the engine, I'd say down around what I paid would be about right. Specs say "O-320-E2D Peterson Conversion", and that the gross was bumped to 1735. I nver heard of the peterson conversion STC so I can't verify that, but I do know some of the engine conversion STC's (like mine) do NOT bump the gross for the 1959-1963 (fastback) models. If you do look into buying a C150/150TD, I'd double-check the empty & gross weights and the CG, as well as look at the wheel alignment (aka toe-in)-- lotsa these airplanes are less than optimal in these two areas.
That said, I really like my airplane. Lots sportier to fly than my old ragwing C170, good performance, and (relatively) inexpensive to operate. Great for solo sport flying, or one or two people with light camping gear-- but if you like a luxury camp better get something bigger.