New to Big Blocks

You have it right on the WP housings and brackets.

1967 and up triangle bracket has a large hole like your photo. It is for access to the wire for the water temp sender. 1966 and back WP housing has the temp sender on the top drivers side. Smack dab under the AC compressor and a pain to get to.

The 1966 and older bracket is solid, no big hole.

The non AC pullies are close together. They can't be mixed with AC pullies, many try it and it's a big mess.