Let me know when you find a block drilled with the "D" 3" spacing.

Will do.

I know I have a 69 “512” block as well as a “351” 67 435, as well as other rat motor blocks, I don’t think I have any early BB. but I have lots of early SB. I will mock it up and check if the hsg fits with all 3 bolts.

Will add to post at a later date, it may be awhile as I’m staying home lately to flatten the curve with this nasty virus.

I amended my post so it does not confuse any one regarding this.

I’ll measure mine shortly!

3 bolt starters are correct for early 409's and maybe early 60's corvettes I believe...…...google part# 1107233 starters - I'm looking for one now.

Yea mine is a early 69 512 block but the starter bolts are 3 1/4” apart!

That's the only way I can measure mine.

OUCH. That sucks big time.

The three hole bolt to the block snouts were used as early as 1957 on Turboglide equipt cars. Have also seen them also used on 409's.

I have an 1107687 starter listed as fitting a 59 and 60 348 Turboglide car. Just measured it and it has 2 7/8" center to center bolt pattern. As I recall, my old 57 Chevy block had the same spacing drilled on the bottom of the block. I had to plug one bolt hole and redrill the block to use a later aluminum starter snout when I was lightening things up on my old drag race stock class drag car.