Does anybody know the thread/diameter/pitch/length of the two lower bellhousing to engine block bolts? There are located at 9 and 3 o clock and have the same 5/8th head. I'm missing one.

 

7/16"-14. I don't recall the length offhand, but do this:
- Measure the thickness of the flange the screw passes through in the bellhousing (the unthreaded hole.)
- Add the nominal diameter (7/16", .4375") to that measurement.
- Select that length of screw or the very next length longer, if it's in between sizes (the thumb rule for maximum strength of a threaded join is 1 to 1.5xd of thread engagement; d being the nominal thread diameter.)