I think before you go tearing into the engine you can do a few basic things first. Remove the prop, make sure it's sitting on the crankshaft boss ok. The spinner and back plate are ok. While the props off check the part number against the type data sheet and make sure the prop is correct for the engine/airframe. You will also be able to find out if it a climb or cruise prop. Refitt it using a calibrated torque wrench with the correct cylinder on TDC. Measure the blades and make sure the are the same length. Once it's all back together check the tracking. I had a 150 with o-200, had vibration at cruise. Removed the prop reseated it and retorqued it and it was fine.
Another couple of things you can do. A compression check. Makes sure you cyclinders have got good compression. Also measure the prop RPM with a prop strobe. This will tell you if your tacho is giving you a correct reading. If your engine has 1400 hrs on it then it shouldn't be that bad. If I remember rightly TBO is 1800 hrs on an O-200