Dual pattern bell housing 200 block years

[lahti35]

I know they started doing the large and small bolt patterns on the back of 200's in '66... but how long did they keep it up? I just saw pictures of a '78 block that had both patterns. Did they have both patterns until the end or was it just hit and miss...

 

[RichCreations]

I know they started doing the large and small bolt patterns on the back of 200's in '66... but how long did they keep it up? I just saw pictures of a '78 block that had both patterns. Did they have both patterns until the end or was it just hit and miss...

i have a dual pattern block from '65, and I think they all were from then, until the low mount starter blocks...