Oldfeller--FSO wrote on 08/03/13 at 19:36:45:The "cracks" your are concerned about are not cracks, they are die check marks left from where the old original 30 year old MOLD has thermal cracked over time. The castings themselves are sound and you will note with your finger that all your "cracks" are positive to the surface of the casting.
They pretty much all look like that. Want to give yourself a heart attack, look at the webbing/crazing inside the clutch case...
The casting flaws will polish off if they bother you.