Ever seen this before?

[Roberts68]

I see what you mean on the T-stat. Since you can't determine if the gasket or cover could have been mishandled, compromised by being unclean mating surfaces etc that lead to failure I understand your decision. I can't help but wonder if that could not have been the case on the rebuild however.

I am in Monticello.

The reason I asked about gearing is I sourced a 12 bolt last summer with 3.55 that originally belonged to a '69 Z-28. I wanted it to still be 3.73 but someone had changed it.
My trans is a TUET11009 /Tremec T56 Magnum, a "close ratio" with a 2.66 1st, .80 5th, .62 6th gear. I am in perpetual build purgatory.

I have done some math or I should say used Tremecs website calculators and really just was curious if 6th will be usable as some people have told me it won't be. Or, at least one engine guru (also old school) told me that it will load up running off idle out of power band or too low on torque curve at cruise rpm etc...

Forgive the thread highjack, and granted you have BIG BBC torque on tap, but could you comment toward this? How do you like it and does this sound like a silly worry?