I bought a 1985 K10 pickup about a year ago from a dealer in Arkansas and learned it had a 396 shoehorned into the engine bay. I've been steadily doing some work on the truck, mostly drivetrain. As I went to swap out the valve covers, I thought I'd learn a little history on the engine, so I went to look at the block stamping on the front passenger side. What I found was definitely NOT a GM code, which leads me to believe the block has been milled...either from heat warping, or for performance reasons.
What's on the block now reads, '391 48 9140
Brad ACH'


Outside of this stamp, the only markings I was able to see was a casting number (was in the iron at the bottom...not a true traceable casting number) on the bottom of the block by the oil pan. This cast was '6T.'


Anyone out there smarter than me (not hard to do!) that can read these tea leaves? Strange marks for sure!

Thanks!!
Sean