If you already have a used one in fairly good condition, you can go to your local autozone, you can buy a brand new block that comes with all the internals and just take all the exterior motor stuff and put it on the new block. My dad and I just did that with my 4banger. Just took it right out the jeep, set it down and tore it apart, as we tore it down we put the parts on the new one.
It costs right around $1000 and if you send them your old block you get about $200 back.