Yeah that's pretty solid, sorry man. With rad empty and coolant in the oil, blown HG or cracked head/block really are your only options. Sounds like it's blown pretty good too. you can do a compression test but I think we all know what it's going to show. That much coolant in the oil is very bad for the rod and crank bearings as well. Keep in mind that these motors have very tight bearing tolerances so the effect is amplified.
At this point I'd start looking into getting another motor. If it's a cracked head or block, you're doing that anyway. If it's the HG, it's probably not worth fixing it not possible without a new head or block.
You did well shutting it down when it got overheated but the fact still remains that it was overheated. As mentioned these motors don't take kindly to that short or not. In my case it was a collision with an animal on the highway. Broke my rad open, lost all the coolant. I too pulled over and shut it off immediately. Didn't matter, still have a slightly leaky HG. Cylinder 2 and 3 show slightly low compression, indicative of a warped head or block. I'm lucky in that it's so mild that it doesn't matter much but you're obviously well beyond that.
If cost is a concern (usually is with a big repair like this) I'd get a used motor from a junkyard. See if you can find one that has relatively low mileage and has been scrapped due to a side impact. If it's head on there's no way of knowing if coolant was lost and it overheated. You may find
www.car-part.com helpful here.
With the design of these motors, a failed HG without some sort of outside cause (like my case) is extremely rare. Unfortunately when they go bad, they go in a bad way. Not easily repaired like older cars that had looser tolerances and a cast iron block.
