With a change in terms to a closed-end, owner-occupied consumer RE loan, would a change in the index from "3 year T Bill" to "NY Prime" require the whole gamut of 266.19 variable rate disclosures or just those applicable to the index change?

Is this a change that is agreed to in writing by the customer for some reason? If not, how are you doing this?

Yes. They want the NY Prime index as that's what was offered by another lender.

I agree. The 3 year T bill is still available and you can't unilaterally change your contract.

If for some reason the consumer is agreeing to this by a modification agreement then you are adding a variable rate feature that has not been previously disclosed therefore this would be a refinancing requiring all new disclosures.