When did Chevy quit drilling oil cooler holes on 4 bolt blocks ?
 

Hi all,
I bought a homebuilt 427 parts motor a couple weeks ago and found the the 289 block is stamped for a '72 Chevelle LS5 (T1112CRW). Surprise #2 was the block is a 4 bolt. My guess is it was converted as the oil cooler holes aren't drilled. I recall factory 4 bolt blocks were drilled up until '74 or so. Am I remembering right ? I'm sure somebody knows off of the top of their head.
Thanks,
Dave