Well it took me a while to see the smoke but it did show itself didn't it!
I can see why you're concerned but it sounds like it'll run a while even if you have to add water every 20 miles or so... you won't know that till you actually give it a test drive. Under pressure it will leak more but you could drive it with the cap loose and just have it leak like it does now.... maybe.
Like Uncle Brad say's get it road ready brakes, wheel bearing repacked or replaced and the other low impact (wallet wise) items that you can check off a to do list and wait for the engine you KNOW you want when it shows itself.
10 hrs of work taking care of some of the things you'll need to do anyway instead of driving all day may help raise your motivation and outlook for the project as a whole, as well as give you a better knowledge of this engine's potential once it hits the road a while. Then decide if you want to stitch this crack or replace the block/complete engine.
KEEP THE WELDER
