New TCI Streetfighter won‘t shift in 3rd when hot

Thank you for posting those pics. They are a perfect example of what I've been talking about on here until I'm blue in the face. Look at the right side of both valve bodies; level with the "O" in the towel. Notice how the left vb has an extension to the right (right above the ptk section); whereas the vb on the right has a cut back area in the same section. That cut back area won't cover a casting pocket in the case. It will allow pressure to bleed off. Look at your two cases and you "should" see how the case matches each vb. They DO NOT interchange. But the good news is now you can air test the clutch drums. You could compare the air pressure test between the two trans. Also check how far those drums will move forward and back. Could you please post pics of the cases where the vb bolt on?