The combination of head casting number (usually on top of the center exhaust ports, a few were on the 'front' (or rear) port) and the head date code (same format as the block date code) will ID which heads it has. Heads differed in valve opening sizes, rocker stud type (screwed in or pressed in) and in some cases, exhaust port configuration.
That block date (June 15, 1969) is very close to the point where the engine foundry would have been switching over to start making engines for the 1970 model year. (See if you can find a large '70' on the top rear of the block nearby the block date code.) In 1970, XH still indicated a Grand Prix with an automatic transmission, same as 69.
On the front of the block, passenger side, down low next to the timing cover, and running vertically, there should be a partial VIN. A "2" followed by the last 8 characters of the VIN number from the car that was built with the engine originally.