If your buddy can shut his hood with the aircleaner, its a 200. This weekend I pulled a 250 out of a 1966. Due to the taller block it does not fit with the aircleaner.
The 250 has the starter down below beside the oil pan. The 200 has the starter up high next to the block.
You can put a 250 head on a 200 block.
BTW the 200 has about 45 more horsepower than the 250.
Well, I had a 200 in my 68 when I got it and it was my daily driver for a couple of years that way, but his seems a lot stronger than I remember mine being. Don't get me wrong, my 200 was a good running smooth engine (I liked it so much that I'm now halfway looking for another classic Mustang to leave a 200 in), but his just seemed a lot stronger.