Mine also cracked, back in the day... but that was about 40,000 kms after a hydrolocking incident.

I'm not sure that 25k is "ok", considering you can get an entire engine for that much... ...but it was freaking hard to find an Exalta head back in the day... most of the heads in the surplus shops are non-VTC.

If your friend wants, he could probably just slot an older head onto the Exalta block. I dunno if the ECU will register the loss of the VTC-equipment as a CEL, but it's worth a shot.