I am a little confused.
When you say you want to buy an engine, that includes the block. You don't need to say block also. You cannot buy an engine without the block. You can buy parts for the engine without the block, but not the whole thing.
And dealing with these cars, you really can't buy a new engine. You would be buying a rebuilt one, and the quality of those is all over the place depending on who does the work and what parts they use.
I hope I come across as trying to help you understand, not as an !@#hole. It sounds like you may be pretty new to all this stuff. Which we all were at some point.
As far as your current engine, like 76hotrodpinto says, unless the inside of the block (cylinder walls, etc) are rusty (which you have to tear the engine apart to see) all you are dealing with is stuff that is easily ( or at least cheaply, mainly your labor and a few dollars in supplies) fixed with some sandpaper/3M pads and paint if everything is working properly.
You may want to replace some things instead of redoing them, depending on cost/ease of removal vs ease of redoing, but for the most part just clean up the rust and repaint. In general, most replacement parts are not as good as the factory originals, so I wouldn't replace stuff that is working well.
If you decide to do this let us know, there are tips and things to avoid we can tell you about. There are definitely some things you do NOT want to get any paint on or in.
Pictures of what you are dealing with would be helpful also.
Russ