I purchased a Cig 28 that had not been winterized properly leading to both blocks cracking. I pulled one out today and it left me wondering about the transmissions. Anything I should check that could have gone bad when it froze?

Check the oil coolers.
Down on side near bottom .
Square plate with 2 hoses coming out of it.
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is this a c-72 borg warner velvet drive trans????

what ever trans it is ,,,,yea ,,as mentioned check the trans oil cooler.

I'm not sure what the application here is. But the plate coolers commonly split along the sides. If it's a tube and shell you may have just popped an end cap or you could possibly have split one of the cooling tubes which is a little harder to tell visually. A quick pressure test should tell. You're not looking for a champagne bubble leak. You'll likely have something significant.