Dont feel bad, we've all been there at one time in our lives. A 327 might be hard to find but obviously an xlnt choice. 327 or 350 first thing I would look for is if the engine has been rebuilt by a competant person with good parts. Then do a compression check, all cyl. should be within 10% of each other. Pull the valve covers to check for crud and sludge build up, pull the dip stick and look at and smell the oil, good indication of how the engine has been maintained. If its still in the car...drive it, look for smoke, engine temp, leaks. If you're not sure take it to someone you trust and have them check it out. If the person thats trying to sell it balks at any of this then walk away and look for another one.