Anything less than a full teardown and rebuild on a 50-year-old engine is a poor choice, if you intend to do anything at all to it. How does it run now? Unless you're able to do a run test on it, including getting it up to normal operating temperature and running it under load at cruise RPM for several miles, the best you have is a "rebuildable core" that needs to be torn down to a bare block and reconditioned accordingly. That can be anywhere from fitting new piston rings, rod and mail bearings, plus a valve job, to reboring the cylinders, new pistons, regrinding the crankshaft, and installing a new cam and lifters, etc. The rebuilding cost can vary from several hundred dollars to several thousand, depending on your ability to do some or all of the work yourself, to hiring it done, including machine work. I do all my own machining, but I've got 60+ years' experience at it, and a shop full of machine tools, including lathes, milling machines, welders, a bead blaster, a valve seat and guide machine, and a crankshaft grinder. Most hobby restorers with the possible exception of Denny Graham, aren't quite that well equipped!
Jerry
