I have done a search and discovered not all small blocks were drilled for both straight and staggered starters. It seems that some have been drilled only for the staggered, particularly 400 small blocks. However, are all blocks with the straight pattern also drilled for the staggered bolt pattern? Are there any drilled only for straight (153 teeth) pattern with no provisions for the staggered pattern (168 teeth). I’m converting from 153 teeth (straight) to 168 teeth flywheel and wondering if I have to check my original 67’ 327 block first. The car is not readily accessible right now (winter storage) checking would be a real hassle.

The last block I remember seeing drilled only for a 153t flywheel/flexplate was a late 50's/early 60's small bore 283 block ...
Every 4" block I can remember seeing was drilled for both.

I'm almost positive that the block will be drilled for both staggered and in line bolt patterns.....At least that's the way it was on a big block Chevelle SS454 I had.

Mark my last small journal 327 was a 67 block and it was drilled for both. If yours isn't and I can't imagine it's not, it would not be hard to drill and tap the block for the staggered pattern starter I wouldn't think. I haven't heard of anyone doing this, but I can't see where there would be any problems in doing it. I know you'd want the hole to be exactly in the correct position so you don't have any problems with the start meshing correctly with the flywheel. But once you figured out exactly where to drill it the rest should be easy.

The cast iron is easy to drill. I drilled and tapped my 400 block for a clutch Z-bar stud so I could run a 4 speed. It was pretty simple to do.

I have three '67 blocks. Two are 327's and one is a 350. All of them have three holes drilled and will work with either starter.

Thanks

the stock 350 in my 74 Monte is only drilled for the large staggered pattern.