John,
Be wary of truck blocks unless you're planning on building a blower motor. They have 2 fly-cut wedges removed from the combustion chamber to lower compression to about 7.5. You can't make that up with different pistons.
There are some ways to recognize a truck motor externally (if it's mostly complete). The intake will be a very low-rise with extra threaded bosses near the front to mount an air brake pump. The dist. is one with a govenor and has a wide metal band around the base. The water pump is huge and the valve covers will have the 4-wire loom tacked at the middle, rather than the rear.
Good luck.
Verne
