If you've got more than $5 million of deferred proceeds across all of your installment sales, you have to calculate interest on the deferred tax. If this applies to you, let me know and I can find you a code section reference and an explanation of how to do the calculation.

An installment sale is not necessarily a reportable transaction for Form 8886 purposes.

Box 17 Code AC is a generic "other information" code, and it's unlikely that it requires overriding.