Glad to hear you are back and running. Some here are saying your block might be bad, I have to say I highly doubt that. First you said they replaced the head gasket BEFORE having verified the squareness of the head. Then the gasket they replaced failed, and THEN they checked the head, (as any competent shop would BEFORE replacing the gasket in the first place).:confused3:

Now, according to the dealer they have milled the head to within acceptable tolerances, (theoretically), and you are now field testing their workmanship.
In my professional opinion, as the owner of a foreign auto repair shop for over ten years, if they did the procedure correctly and the head checked out as true by their machine shop you should have no further problems with this engine for a reasonable lifespan of a diesel tractor engine.
I'm also saying not to worry about the block, the likely hood of it being warped is minuscule at 50 hours.
If they replaced the head bolts, as you stated they told you they would, then find out when they need to be retorqued. If they can't answer that question to your satisfaction, I would contact Kioti Corporate and
detail your concerns to their zone representative by phone AND in writing.
Keep any receipts you received from the dealer for all repairs related to this issue, FOREVER!
Check fluids regularly, and do so with coolant level as well as oil. Check the interface between the block and head for any signs of weeping or leaks too.
How much time is left on the warranty? If this repair was close to end of your warranty, which I doubt, due to 50 hours on the machine, you should have the dealer explain how long the repair is warrantied by them; usually to end of your factory warranty, or a stated term beyond same if close to termination of factory warranty.
Otherwise I would not sweat the thought of a block, or especially a new engine- that's NEVER going to happen if they can fix it with a head plane and gasket and bolts. You'd have to have a catastrophic failure for that to even come onto the radar.