Over heated now there is a coolant leak

I overheated my truck and had to drive it a little farther than I should have to get to a safe place before stopping (my home). This was late at night. The next morning I filled the radiator with water and found that the water just poured out of the engine (not the radiator).

I am assuming one of two things: either I blew the head gasket or I cracked the block. I have not taken it to the mechanic yet due to towing costs, etc.

Several days later, I needed to move the truck over about a foot so I clenched my teeth and turned the key to see if I could accomplish that task. It started right up and I was able to back it a few feet and move it over. I did not drive it anywhere and do not plan to.

My question: Does the fact that it actually started after such a fiasco indicate that it might only be the gasket and not the block? And are there also other possibilities?