Kapp the 30 below the 352 is just the block mold number. The 352 was just an identifier used on the block besides the later reverse 105. Besides checking the cyl bore you also want to gap the cyl wall cores. This will further help to tell what block you have. Sonic checking is the absolute best way but this is a quick and easy identifier. I can fill you in if interested.

Snake, I figured you meant 66. I've done the same many, many times. Fingers faster than the brain in my case. LOL. G.