I think I would get a second or third opinion on that engine repair. There are good quality engine rebuilders around that can do very good work on cast blocks. I think some call it cast stitching. As with most things there are no guarantees but at least you aren't missing parts. Of course if a Buda deisel engine from a Cockshutt 30 is available you may still have to have that one rebuilt.
Just my 2 cents.