If I bought a used pair of cylinder heads, besides buying bolts and the like would i need to do anything else to them, like get them machined or anything??
Personally I would have a machine shop look them over before installing them. You might end up needing a valve job or something. Better to know before they go on the car. Also if you are considering upgrading the came in the future now is the time to replace the valve springs. Depending on what size cam you are looking at I would recommend the Trickflow kit from summit.
The above is pretty much what I did when I bought my used P heads. Now I just need the time to put them on the car.