Well it will not be a bolt in. You are going to need to align the front sprocket to the rear and then weld in some tabs and spacers to bolt things up. Roomwise, you should be fine in the frame I think.
I would suggest making a ceiling hoist to hold the engine while to work on things. Dont for get hangers for your exhaust and carbs.
If you are not up for all this work, I suggest a different 79-82 cb engine then as they should all be pretty close to a drop in.
Price for a new engine(to you) will probably run 200 or so.
What is wrong with the old engine?
The ride IS the adventure. The destination is just to get gas!