The earlier C-172 models fitted with the 0-300-D engines are delightful gentle aircraft with a very very smooth engine. Of course slightly underpowered (hence the upgrade in later models from the 145hp in the 0-300-D to 150hp in the first of the lycomings and then 160hp in later models still. These later models were eventually heavier and hence needed the bigger engine to maintain (or slightly improve ) the performance.
An early model with the 0-300-D is a very cheap and good way into 4 seat touring aircraft(but watch the (W and B). Cheap to buy, negative depreciation, easy maintenance,happy on mogas, cheap to insure, occasional problems with sticky exhaust valves but with considerate engine management there should be no problems.
Go for one.