BigRigTech
Diesel junky
Some do pass through into the block.
I drilled the trans case last night....I had to open the 2 top holes up to 1/2",then I bolted on the spare adapter using the top two holes and drilled through the adapter for a guide....Everything went ok from what I could see.....The dowel holes are 3/8"....I just have to to do the same to my tin spacer plate as well.

....The adapter plate work's A1 for a drill guide....I was going to chop the bottom of the tin plate off for a clutch cover....I will have a good 12" clutch to sell, like new and a 11" T19 clutch disc -also like new if anyone wants it cheap. Goofy is out in the shop working on the truck, I have to wait until all the kiddies are asleep.