How deep can I go? There looks like there is a pressed in plug where I need to drill, can this be extracted? My trans is a tailshift (think the inter-plates are the same anyway)
I'm planning to make the post out of a piece of silversteel and press it in -did the factory do this or thread the post on the 914-6?

The post is threaded 8mm x 1.25, threaded section is 14mm long, your hole will have to be deeper and threaded with a bottoming tap.

If a tail shift the hole for the stud is already there!

The hole goes as deep as the perpendicular hole for the underlying stud from the case to the tail cone. The hole should be there already. I used a spare tranny case stud and it has worked well.

Thanks for the reply's (couldn't have asked for 3 more knowledgeable guys )
My hole seems to have a plug in it (cue laughter). I might try and pull it with a slide hammer but basically I can drill this out down to the through stud if I'm understanding you correctly.

What is "silversteel"? The Cap'n

cold roll

From your photo it may be a plug. You would have to drill well undersize to ensure that if there are threads in there, then they are not damaged. I would remove that stud to prevent damage should you have to drill through, and also to provide room for the end of the drill bit and the end of the tap should you require them. I wonder how far into 1972 MY they drilled and tapped those holes. The 914/6 ended so early that those operations were wasted.

Silversteel is sometimes called bright steel, basically high carbon steel that doesn't rust easily and machines well. I think it used to be used to make razors becasue it holds a fine edge