I have ground down a 3/8 extention to fit

I also used a torch to get it cherry red and then hit it with the 3/8 drive air hammer with extention

after they are out,and you buy a complete core plug kit(I prefer brass core plugs for the block)those are replaced with allen plugs that a regular allen wrench fits

i have the part # at home for a complete kit,which also comes with a oil pump drive bushing for the block as well

I will post it later