A new timing set is cheap and easy to install. You will have more trouble getting the oil pan to seal on the timing cover. I would be inclined to pull the oil pan (jack engine up first for clearance) and install a new full pan gasket. That would give a chance to inspect the lower end. You can even change the rod and main bearings, and rear seal from below; at least I did on my 383.
If you don't want to invest $15 in a HF compression gage kit, you can get a good feel for the engine's quality by turning it over by hand. If you must fight 3 good "air springs" each rev, you know compression is good. If you hear each one hold pressure and hiss down over <10 secs, that is "like new" condition.
Don't believe that dropping a small block in is as easy or cheap as others suggest. That takes a lot of parts and fairly high skill.
