Tremec TKO to Ford FE - Input Shaft

[HSSS427]

This has been bugging me for a while, so figured a picture is worth a thousand words. Below is a diagram I made trying to determine what clearance I had between the input shaft on my Tremec TKO 600 and the crank on my 427 so. I learned the hard way that an input shaft that is too long = torn up thrust bearings, pain and agony.

I now have a short shaft installed, and understood that I would not require a spacer between the tranny and Lakewood scattershield when I used this. However, when I originally installed it, I couldn't get the input shaft to seat far enough down in the pilot bearing to get the tranny butted up against the scattershield. Based on past experience I also didn't want to force it together for fear of bottoming out in the crank.

So, installed it with the 5/8" spacer and all appeared fine. Have the engine out for other reasons, but am now concerned that I'm not getting enough engagement of the input shaft into the pilot bearing.

So, assuming I have my dimensions correct, it appears there's no way to use the longer input shaft as it's longer than the total distance from tranny face to block face. I also can't use the short input shaft without the spacer as it is longer than the depth of the scattershield plus block plate, thus appearing to invalidate the idea of using a short input shaft without a spacer.

So now the thing I don't know if how far away from the block face is the bottom of the hole in the end of the crank, and how far from the block face is the surface of the crank flange. If I have this, I can tell how much engagement of the input shaft I'm getting.

I am not and engineer, but play one when I'm in the garage. Appreciate comments, observations and corrections to my diagram to help clear this up.