I always enjoy disassembling an engine (unless of course I had just assembled it... =P )
For the pistons, clean the carbon off the tops and if its been bored you should find a stamping on them showing a number for its over size. Some of them get fuzzy with use, but out of six pistons at least one will be readable. If you cannot find a stamping on any of them, its a very good chance they are standard bore.
Here are the stampings on my OHC L6. They are easier to read in person than in the photos.
Right at the top of the picture.
And these pistons were crusty. I used a wire wheel to clean them, but brake clean and a scotchbrite pads can get you there. This engine had two different styles of pistons in it for some reason. Both were 0.030" over bored. When I first pulled the head off I was expecting the two different pistons to be a different size =P
