I am kinda confused here, is there anyway to tell a 325 HP 396 Block from a 375 HP 396 Block, now I am talking about bare blocks here so is there anyway to know?

the 325 hp block is a 961 and the 375hp will be a 962

I only have this number for the block 3955272

I only have this number for the block 3955272
3955272 1969 396 / 402 325 / 350 / 375 hp 2 & 4 bolt

I think the differencs between the 325/375HP :
the 325HP had a stock comp ratio of 10.25
the 375HP had a stock comp ratio of 11
The 325HP usually came with Oval intake and heads
The 375HP usually came with Rect intake and heads
same 4.094 bore
same 3.76 stroke
same crank
375HP had a hotter spark plug
375HP usually had a alloy or Aluminum intake
375HP usually came with a Holley carb
325HP usually were Q-jet

Just a little info, I am sure others will chime in.

Didn't all the 375hp motors have 4 bolt mains?

Mike, one of my books also has a 962 casting for the 360 horse 4bolt main produced in the 66 Chevelles. I owned a couple of these (back in the day). Sure wished I"d have kept 'em!!!!!!!

Mike, one of my books also has a 962 casting for the 360 horse 4bolt main produced in the 66 Chevelles. I owned a couple of these (back in the day). Sure wished I"d have kept 'em!!!!!!!

The 360 HP that I had back in the day was a 2-bolt main. Maybe this was the exception, but it was original.

The 375 HP block alone will have 2 distinct features. It will be a 4 bolt main block and by the oil filter, 2 of the bosses will be drilled and tapped so an external oil cooler could be used if someone were to want one. Here's a picture of the tapped bosses.