S6 crankcase bolts, 3/8 or 5/16?

[Doug]

Recently I had a query about S6 crankcase bolts. I have seen these where the timing cover end is threaded 3/8-20 and also 5/16-22. The other end that holds the crankcase halves together is always 3/8-20. I thought at first the 5/16-22 was a repair; someone turned down the original bolts to renew a damaged thread. But the query reported 5/16-22 threads too, with holes drilled in the bracing plate and timing cover to suit. 

So the question is, did they change the stud diameter on the timing cover side during the production run? Did they go from small to large, or large to small?

-Doug

[ManfrerdSt]

Hello Doug,
   Here is my tax-housing cover.